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Genetic classification of Pc3 and Pc4 geomagnetic pulsations in mid-latitudes Ng, Tai Ping 1969

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GENETIC  CLASSIFICATION  GEOMAGNETIC  PULSATIONS  OF  Pc3  AND  Pc4  IN  MID-LATITUDES  by TAI  PING  NG  A.R.M.I.T.,  Royal Melbourne I n s t , of Technology,  1961  M.Sc,  The U n i v e r s i t y  1966  A THESIS SUBMITTED  of B r i t i s h Columbia,  I N PARTIAL FULFILMENT OF  THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF  PHILOSOPHY  i n the Department of GEOPHYSICS  We a c c e p t t h i s t h e s i s a s c o n f o r m i n g t o t h e required  standard  THE UNIVERSITY OF B R I T I S H November,  1969  COLUMBIA  In  presenting  this  an a d v a n c e d  degree  the  shall  I  Library  further  for  agree  scholarly  by  his  of  this  written  thesis  in p a r t i a l  fulfilment  of  at  University  of  Columbia,  the  make  tha  it  permission  available  for  It  financial  is  gain  of  The U n i v e r s i t y o f B r i t i s h V a n c o u v e r 8, C a n a d a  by  the  Columbia  shall  not  requirements  reference copying o f  I  agree  and  copying or  be a l l o w e d  for  that  study.  this  thesis  Head o f my D e p a r t m e n t  understood that  permission.  Department  for  for extensive  p u r p o s e s may be g r a n t e d  representatives. thesis  freely  British  the  or  publication  without  my  i l  ABSTRACT  Dynamic s p e c t r a p r o c e s s e d f r o m d a t a magnetic tape a t t h e m i d - l a t i t u d e R a l s t o n i n 1967 h a v e b e e n s t u d i e d i n d e t a i l .  r e c o r d e d on station  The Fc3,k  a p p e a r t o b e h a v e i n a much more c o m p l i c a t e d reported  by other  observers  v a r i a t i o n o f t h e Pc3,k  (Alberta)  pulsations  manner t h a n  a t l o w - l a t i t u d e s t a t i o n s . The  frequency a t Ralston  assumes d i f f e r e n t  f o r m s f r o m one d a y t o a n o t h e r , t h e p a t t e r n  depending  l a r g e l y upon t h e g e n e r a l  disturbance  represented  by the Kp-index.  most o f t h e Pc3,k one  l e v e l o f magnetic  I t appears, however,  spectra analysed  may be c l a s s i f i e d  p r e t a t i o n i s o f f e r e d t o e x p l a i n the 'existence  crux  into  of, o r a combination of, four w e l l - d e f i n e d d i u r n a l  p a t t e r n s under steady magnetospheric c o n d i t i o n s .  the  that  fine  An i n t e r -  as w e l l as  s t r u c t u r e o f these four d i u r n a l patterns.  o f the present  i n t e r p r e t a t i o n i s that Ralston,  The under  m o d e r a t e m a g n e t o s p h e r i c a g i t a t i o n , may p i c k up m i c r o p u l s a t i o n a c t i v i t i e s o r i g i n a t i n g from t h e plasmasphere  and/or  the p l a s m a t r o u g h d e p e n d i n g upon i t s p o s i t i o n r e l a t i v e t o the plasmapause.  Eigen- o s c i l l a t i o n s o f m o d i f i e d  Alfven  mode ( p o l o i d a l o s c i l l a t i o n ) i n t h e s e two m a g n e t o s p h e r i c regions  are considered  t o be t h e p r i m e s o u r c e s o f t h e g r o u n d  o b s e r v e d Pc3*4 m a g n e t i c p u l s a t i o n s . r e i n f o r c e d by observations mid-  Such s u g g e s t i o n i s  made s i m u l t a n e o u s l y  and h i g h - l a t i t u d e s t a t i o n s .  Other  p r o p e r t i e s o f Pc3 and Pc4 a r e d i s c u s s e d t h e new i n t e r p r e t a t i o n .  a t other  morphological i n the l i g h t of  iii  TABLE  OP  CONTENTS PAGE  ABSTRACT  i  i  L I S T OP FIGURES  v i  L I S T OP TABLES  x i  ACKNOWLEDGEMENTS  x i i 1  CHAPTER I  GENERAL INTRODUCTION  CHAPTER I I  SOURCE OP DATA AND INSTRUMENTATION  15  11.1  Source o f Data  15  11.2  R e c o r d i n g and R e p r o d u c i n g S y s t e m  22  11.3  Tape A n a l y s i n g S y s t e m  26  CHAPTER I I I  S U B C L A S S I P I C A T I O N OP Pc3 I N MID LATITUDE - DIURNAL V A R I A T I O N OF PC3 FREQUENCY AT RALSTON  29  111.1  Introduction  29  111.2  Multi-Band Pulsation  33  111.3  N o r m a l Type w i t h M o r n i n g a n d Afternoon Separations  4-2  111.4  The I n v e r t e d U-Type w i t h Structure  51  111.5  The D i f f u s e d I n v e r t e d U-Type  54  111.6  Mixed Cases o f the Pour B a s i c Type s  60  111.7  Miscellaneous  70  111.8  I n t e r p r e t a t i o n o f R e s u l t s and Discussion  Structured Continuous  Discrete  Types  75  iv  CHAPTER I V  Kp-DEPENDENCE OP P c 3 I N MID LATITUDES ^  83  IV.1  Introduction  IV.2  Kp-Dependence o f t h e Pc3 F r e q u e n c y  86  IV.3  S u d d e n E n h a n c e m e n t o f Pc3 A c t i v i t y  101  IV. 4  Discussion  106  COMPARATIVE STUDIES OP Pc3 I N HIGH AND MID LATITUDES  CHAPTER V  83  110  V. l  Introduction  110  V.2  L a t i t u d e D e p e n d e n c e o f Pc3 F r e q u e n c y - P r e l i m i n a r y O b s e r v a t i o n s on R a p i d Run M a g n e t o g r a m s  115  D i u r n a l V a r i a t i o n o f Pc3 a t a H i g h L a t i t u d e S t a t i o n - G r e a t Whale R i v e r ( G e o m a g n e t i c <f) = 66.6°, L=7.5)  122  V.4  L a t i t u d e D e p e n d e n c e o f Pc3 F r e q u e n c y  132  V.5  C o n j u g a c y o f Pc3 a t H i g h and M i d Latitude  144  V. 6  Discussion  150  V.3  CHAPTER V I  GENERAL STUDIES  OF Pc4  VI. 1  Introduction  VI.2  D i u r n a l V a r i a t i o n o f Pc4 a t t h e  VI.3  I56 156  Mid-Latitude Ralston Station  159  L a t i t u d e Dependence o f Pc4  166  VI.4 Discussion CHAPTER V I I POSTSCRIPT: DISCUSSION AND FUTURE EXPERIMENT  172 174  V  BIBLIOGRAPHY  178  APPENDICES: Appendix 1  C h a r a c t e r i s t i c s o f t h e Plasmapause  Appendix 2  S p e c i f i c a t i o n o f Kay E l e c t r i c Sonagraph  Appendix 3 Appendix 4  7029A  P o s s i b i l i t y of Multi-Band Caused by Harmonics  I83  I85  Pc3  Table of the K Index f o r Dates Illustrated in^Figures  186  189  LIST  CHAPTER  OP  FIGURES  I  FIG  1.1  Magnetospheric F i e l d Configuration  PIG  1.2  Equatorial Alfven V e l o c i t y of the Magnetosphere  FIG  1.3  T h e o r e t i c a l E s t i m a t i o n o f Dependence o f Pc2, 3 and 4 p e r i o d i n t h e p l a s matrough on M a g n e t i c A c t i v i t y ( a f t e r T r u s s e l , 1966)  CHAPTER  Line  II  PIG  II.la  S t a t i o n s from which were O b t a i n e d  Magnetograms  FIG  II.2a  F r e q u e n c y R e s p o n s e o f t h e PM B r o a d Band R e c o r d i n g System  II.2b  FM-Micropulsation Recording  System  CHAPTER I I I FIG  PIG  III.2a  R a l s t o n Y, S e p t , 18, 1965 M u l t i - p e r i o d i c i t y o f Pc3  III.2b  R a l s t o n Y, F e b . 11, 1967 M u l t i - b a n d Pc3 w i t h D e c r e a s i n g F r e q u e n c y f r o m Dawn t o Dusk  III.2c  R a l s t o n Y, F e b . 12, 1967 M u l t i - b a n d Pc3 w i t h C o n s t a n t Frequency  III.2d  R a l s t o n X, Nov. 15, 1967 M u l t i - b a n d Pc3 i n t h e E a r l y  III.2e  R a l s t o n X, D e c . 6, 1967 4 b a n d s s t r u c t u r e d Pc3*^  III.3a  R a l s t o n X, O c t . 18, 1967 N o r m a l Type w i t h M o r n i n g and Afternoon Separation  Morning  vii  FIG  FIG  III.3b  R a l s t o n X, D e c . 7, 1967 N o r m a l Type under. D i s t u r b e d C o n d i t i o n s  47  III.3c  R a l s t o n X, F e b . 10, 1967 N o r m a l Type u n d e r Q u i e t C o n d i t i o n s  48  III.3d  R a l s t o n X, O c t . 30, 1967 A f t e r n o o n Type o f P c 3  49  III.3e  R a l s t o n X, M a r . 19, 1967 The ' P a u s e ' t h a t O b s e r v e d i n t h e Morning  50  R a l s t o n X, M a r . 26, 1967 I n v e r t e d U-Type w i t h D i s c r e t e Structure  52  R a l s t o n X, D e c . 28, 1967 I n v e r t e d U-Type w i t h D i s c r e t e Structure  53  R a l s t o n X, O c t . 16, 1967 I n v e r t e d U-Type w i t h D i f f u s e d Structure  57  R a l s t o n X, Nov. 19, 1967 D i f f u s e d Type o f D i u r n a l S t r u c t u r e  58  R a l s t o n X, Nov. 17, 1967 D i f f u s e d I n v e r t e d U-Type w i t h S e c o n d a r y Maxima  59  R a l s t o n X, S e p t . 7, 1967 Combination of the D i s c r e t e Inverted U-Type and t h e M o r n i n g and A f t e r n o o n Type  65  R a l s t o n X, O c t . 4 , 1967 M i x e d I n v e r t e d U-Type o f D i s c r e t e and D i f f u s e d S t r u c t u r e  66  R a l s t o n X, O c t . 26, 19.67 M i x e d I n v e r t e d U-Type o f D i s c r e t e and D i f f u s e d S t r u c t u r e  67  III.6d  R a l s t o n X, O c t . 25, 1967 M i x e d I n v e r t e d U-Type and N o r m a l Type  63  III.6e  R a l s t o n X, S e p t . 1 , 1 9 6 7 Mixture of a l l 4 basic types  69  III.4a  III.4b  FIG  III.5a  III.5b III.5c  FIG  III.6a  III.6b  III.6c  VI11  P I G  I I I . 7 a  I I I . 7 b  1 1 1 . 7 c  I I I . 7 3  C H A P T E R P I G  R a l s t o n X , F e b . 23, M i s c e l l a n e o u s T y p e s  19^7  R a l s t o n X , O c t . 12, M i s c e l l a n e o u s T y p e s  1967  R a l s t o n X , M a r . 18, M i s c e l l a n e o u s T y p e s  1967  R a l s t o n X , O c t . 29, M i s c e l l a n e o u s T y p e s  1967  I V . 2 a  £ l C  D e p e n d e n c e F r e q u e n c y  o f  t h e  P c 3  K p  I V .  2c  R a l s t o n ^ = 0  X ,  N o v .  18,  1967  I V .  2 d  R a l s t o n  X ,  M a y ,  10,  1967  I V .  I V .  I V .  D e p e n d e n c e  -  a t  M e a n  0 =  R a l s t o n  94  58.8°  95 96 97  1  2e R a l s t o n  X ,  O c t .  5,  R a l s t o n  X ,  M a r .  27,  98  1967  2 f  2 g  I V . 3 a  I V .  F I G  74  2b  I V .  C H A P T E R  73  I V .  "P  P I G  72  I V  p  .  71  3 b  3 c  *P -  1967  99  .  3  1 0 0  R a l s t o n X , D e c . 26, R a l s t o n X , A u g . 9, N o S u d d e n E n h a n c e m e n t  1966 1967 o f  R a l s t o n X , M a y 22, S u d d e n E n h a n c e m e n t  o f  1967 P c 3  R a l s t o n X , A u g . 23, S u d d e n E n h a n c e m e n t  o f  1967 P c 3  103  P c 3  1 0 4  a n d  P c 4  105  V V . 2 a  D e c e m b e r  17,  1965  V . 2 b  F e b r u a r y  17,  1967  V . 2 c  Pc3 M o d u l a t e d P e l , A u g u s t 2 2 , 1966  = K p  =  G r e a t  0  119  +  3  Q  W h a l e  1 2 0 X , 1 2 1  D i u r n a l Regions  at Great  Whale  G r e a t Whale-, S e p t e m b e r 20, 1965 P o s i t i v e B a y A s s o c i a t e d Pc2,3 G r e a t W h a l e , December 19, 1965 N e g a t i v e Bay A s s o c i a t e d Pc2,3 S e p t e m b e r 18, January of  21,  1965,  1964,  Pc3,4  April  18,  1964,  Impulsive  L a t i t u d e Dependenc  Pc5 w i t h P c 3  Multi-band  Structured  Pc3  Multi-band  Structured  Pc3  O c t o b e r 18, 1967, L a t i t u d e o f N o r m a l Type o f P c 3 S e p t e m b e r 19, Mid-Latitudes  Events  1965,  Riders  Dependenc  Pc3 a t t h e  F e b r u a r y 26, 1967, S i m u l t a n e i t y o f t h e I n v e r t e d U-Type o f P c 3 a t M i d and H i g h - L a t i t u d e s L a t i t u d e Dependence o f Pc3 C o n j u g a c y o f Pc3 C o n j u g a c y o f Dawn a n d D u s k Type Pc 2,3 S e p t e m b e r 16, 1965, C o n j u g a c y o f Pc3 a t H i g h and M i d L a t i t u d e s Conjugacy under Disturbed  Conditions  R a l s t o n X, F e b r u a r y 24, 1967 D i u r n a l V a r i a t i o n o f Pc4 R a l s t o n X, November 9 , 1967 S i m u l t a n e o u s O c c u r r e n c e o f P c 3 and Pc4 R a l s t o n X, November 13, Pc4 i n t h e A f t e r n o o n  1967  X  FIG  VI.2d  C o m p a r i s o n o f t h e X and Y  Field  Components FIG  165  VI.3a  Pg A c t i v i t y  at M c G i l l  169  VI.3b  C o n j u g a c y and L a t i t u d e D e p e n d e n c e of Pc4 L a t i t u d e Dependence o f P c ' s  171  VI.3c  170  xi  LIST  OP  TABLES  TABLE 1.1 11.1  11.2  111.1  111.2 111.3  IV.1  PAGE C l a s s i f i c a t i o n of Micropulsations The L o c a t i o n a n d M a g n e t i c E l e m e n t s o f S t a t i o n s f r o m w h i c h D a t a was Made A v a i l a b l e  19  S e l e c t e d Data Used i n t h e P r e s e n t Investigation  20-21  C h a r a c t e r i s t i c s of Clear Multi-Band Continuous P u l s a t i o n a t Ralston i n  1967  35  D a t e s o f D i f f u s e d I n v e r t e d U-Type D i u r n a l V a r i a t i o n of Frequency  55  S u b - C l a s s i f i c a t i o n o f Some Pc3 Events Dependence o f D i u r n a l  62-64  Variation  P o f Pc3  V.l  2  L a t i t u d e D e p e n d e n c e o f Pc3 R e p o r t e d by Data Observer  87-88  155  xii  AC KNOWLBDGEMENTS  I  w i s h t o e x p r e s s my s i n c e r e t h a n k s t o D r . T. W a t a n a b  for  h i spatient  for  many h o u r s  investigation. suggestions, reviewing I recently  study  of discussion I am d e e p l y  criticisms,  guidance,  during the course indebted  also  tape  wish  t o thank  D r . J . A. J a c o b s f o rtheir  and f o r p r o v i s i o n  i n t e r e s t and  o f an atmosphere  conducive  o f D r . J . K. P e t r i e i n I. w o u l d  like to  f o r arranging the use o f t h e Sanborn  recorder.  equipment  am d e e p l y  indebted  Pacific  essential  am m o s t g r a t e f u l  t o t h e Defence  f o rproviding data  to this  investigation.  t o S i r Charles Wright,  Research as w e l l  as  In particular, Mr. A. S h a n d ,  K. C. M a c l u r e , a n d M r . C. Gibbs o f t h e D . R . E . P . who h a v e  given  so much o f t h e i r  investigation Thanks for  a n d more  constant  r e v i e w i n g o f the m a n u s c r i p t .  Establishment,  Dr.  valuabl  and r e s e a r c h .  D r . R. M. E l l i s  I  I  many  and comments and f o r c a r e f u l  D r . R. D. R u s s e l l  careful  thank  an  ofthe  t o him'for  I' a p p r e c i a t e t h e v a l u a b l e h e l p her  and encouragement,  of the manuscript.  encouragement tc  supervision,  their  a n d a s s i s t a n c e t o make  this  possible. a r e d u e t o D r . D. S m y l i e  helpful  manuscript.  time  comments i n t h e f i n a l  a n d D r . T. U l r y c h preparation ofthe  H e l p f u l d i s c u s s i o n s are colleagues, M.  in particular,  B e r r e t t a , R. This  grant t o Dr.  provided T.  M e s s r s . K.  M i c h k o f s k y and  study by  was  acknowledged w i t h  partially  R.  R.  Roxburgh,  Olowin.  s u p p o r t e d by  a  research  the N a t i o n a l Research C o u n c i l of  Wa'tanabe.  my  Canada  CHAPTER GENERAL  At the 13th  General  I  INTRODUCTION  Assembly of the I n t e r n a t i o n a l 1963,  Union of Geodesy and G e o p h y s i c s i n B e r k e l e y , August  the n o t a t i o n and c l a s s i f i c a t i o n of geomagnetic m i c r o p u l s a t i o n s were d i s c u s s e d by Committee 10 of the I n t e r n a t i o n a l A s s o c i a t i o n of Geomagnetism and Aeronomy. e x p e r i m e n t a l knowledge o b t a i n e d  Prom the  s i n c e the I n t e r n a t i o n a l  G e o p h y s i c a l Year, i t has been r e c o g n i z e d t h a t m i c r o p u l s a t i o n s can be d i v i d e d i n t o two main c l a s s e s : a r e g u l a r , and m a i n l y c o n t i n u o u s ,  those  of  c h a r a c t e r and those  with  an i r r e g u l a r p a t t e r n (Jacobs e t a l , 1964). The Table  1.1.  c l a s s i f i c a t i o n scheme then proposed i s l i s t e d i n The  r e s e a r c h t o be p r e s e n t e d  i n this thesis i s  p r i n c i p a l l y concerned w i t h the P c 3 , 4 band of  continuous  micropulsations. S i n c e g r e a t advances have been made i n the p a s t y e a r s i n the f i e l d of m i c r o p u l s a t i o n r e s e a r c h and  in Its  r e l a t e d f i e l d s , t h i s c l a s s i f i c a t i o n can, of c o u r s e , improved.  In p a r t i c u l a r , a b e t t e r understanding  be  of the  g e n e r a l p h y s i c a l s t a t e of the magnetosphere and of morphological  five  p r o p e r t i e s of m i c r o p u l s a t i o n s e n a b l e s  the one  to  d e f i n e more a c c u r a t e l y the range of p e r i o d s f o r a number of groups.  For. I n s t a n c e , i t i s now  a well-known f a c t t h a t  2  there  exist  frequency to  many d i f f e r e n t  types of pulsations  range d e f i n i n g t h e P e l g r o u p .  subclassify Pel accordingly  1967j  This  e n a b l e s one  ( S a i t o , 1964a;  Troitskaya,  etc.).  TABLE CLASSIFICATION  Type  MICROPULSATIONS  Range o f P e r i o d s ( S e c )  Pc2 Pc3 Pc4 Pc5  Irregular  1  Pil  Pi2  40  200 100 22 6.7 1.7  one o f t h e o l d e s t  i nmicropulsation  pulsations  with  a period  -  40 - 150  25 6.7  and y e t t h e l e a s t  research. o f about  was n o t u n t i l  momentum g a t h e r e d  very  known  Eschenhagen  observed  30 s e c o n d s a t Potsdam, 1957b), b u t  r e c e n t l y , m a i n l y due t o t h e r e s e a r c h  since  morphological properties Even today,  - 1000 25  micropulsations  Germany a s e a r l y a s 1896 ( K a t o and Watanabe, it  - 5000 - 2000 - 100 22 6.7  Pulsations  Pc3,4 b a n d s o f c o n t i n u o u s  The  f (mHz)  ,  Pulsations  0.2 5 5 - 1 0 1 0 - 4 5 45 - 150 150 - 600  Pel  represent  I.1  OF  Continuous  field  within the  when n e a r l y  t h e IGY, t h a t  some o f t h e  o f Pc3,4 became b e t t e r a decade h a s e l a p s e d  known.  since  the epoch  3  of space e x p l o r a t i o n , some of t h e i m p o r t a n t p r o p e r t i e s o f Pc3,4 such as t h e d i u r n a l v a r i a t i o n o f f r e q u e n c y ,  latitudinal,  l o n g i t u d i n a l and K -dependence, e t c . , remain a m a t t e r o f controversy.  Prom time t o time a p p a r e n t l y c o n t r a d i c t o r y  r e s u l t s have been r e p o r t e d by d i f f e r e n t e x p e r i m e n t e r s and t h e r e i s n o t y e t a c o n s i s t e n t model t h a t c o u l d e x p l a i n t h e s e differences. The s c a r c i t y o f s u f f i c i e n t l y h i g h q u a l i t y d a t a and t h e inadequacy  of the s p e c t r a l a n a l y s i s  techniques  employed have been r e c o g n i s e d as two p r i n c i p a l reasons f o r the e x i s t e n c e o f some o f t h e i n c o n s i s t e n c i e s .  Although  c h a r t magnetograms have y i e l d e d so much i n f o r m a t i o n i n t h e past and w i l l c o n t i n u e t o do so i n the f u t u r e , s c a l i n g o f c h a r t - r e c o r d e d magnetograms may o f t e n be m i s l e a d i n g p a r t i c u l a r l y when more than one f r e q u e n c y component i s involved. developed  V a r i o u s s p e c t r a l a n a l y s i n g t e c h n i q u e s have been r e c e n t l y i n m i c r o p u l s a t i o n r e s e a r c h , one o f t h e  most s u c c e s s f u l b e i n g dynamic spectrum  a n a l y s i s o f magnetic  t a p e - r e c o r d e d d a t a , used, f o r example, i n the d i s c o v e r y o f hydromagnetic  e m i s s i o n s ( S a i t o , i 9 6 0 ; T e p l e y and Wentworth,  1962).  I n t h e p a s t t h r e e y e a r s t h i s new s p e c t r a l a n a l y s i n g t e c h n i q u e has been extended regions.  Hirasawa  t o many o t h e r lower  and Nagata (1966),  frequency  and Nagata and  F u k u n i s h i (1968) among o t h e r s , were s u c c e s s f u l i n p r o d u c i n g dynamic s p e c t r a o f Pc3,4 and they observed  a certain  regularity  4  i n the d i u r n a l v a r i a t i o n o f f r e q u e n c y i n each o f t h e s e bands. T h e i r r e s u l t s , however, a r e based o n l y on an a n a l y s i s o f magnetic d a t a from l o w - l a t i t u d e s t a t i o n s . As d i s c u s s e d  i n Chapter I I I , dynamic s p e c t r a p r o c e s s e d  from magnetic t a p e s r e c o r d e d  a t the m i d - l a t i t u d e  Ralston  s t a t i o n ( A l b e r t a ) i n 1967 have been s t u d i e d i n d e t a i l .  More  t h a n 500 sonagrams have- been s t u d i e d , and t h e Kay E l e c t r i c Sonagraph 7029 w i t h s c a l e expander p r o v i d e s  a marked  improvement i n the q u a l i t y o f these sonagrams.  The r e s u l t s  i n d i c a t e t h a t P c 3 , 4 observed i n m i d - l a t i t u d e s behaves i n a much more c o m p l i c a t e d  manner t h a n r e p o r t e d by Hirasawa and  Nagata (1966) a t t h e l o w - l a t i t u d e s t a t i o n .  The v a r i a t i o n  of the P c 3 , 4 f r e q u e n c y a t R a l s t o n assumes d i f f e r e n t forms from one day t o another, t h e p a r t i c u l a r p a t t e r n depending l a r g e l y upon the g e n e r a l l e v e l o f magnetic represented  by the K^-index.  I t appears, however, t h a t  most o f t h e P c 3 , 4 s p e c t r a a n a l y s e d one  disturbance  may be c l a s s i f i e d i n t o  of, or a combination of, four w e l l - d e f i n e d d i u r n a l  p a t t e r n s under steady magnetospheric c o n d i t i o n s .  An  i n t e r p r e t a t i o n i s o f f e r e d t o e x p l a i n the e x i s t e n c e as w e l l as t h e f i n e s t r u c t u r e o f these f o u r d i u r n a l p a t t e r n s . As m i c r o p u l s a t i o n s  are known t o be o f magnetospheric  o r i g i n , the morphology o f Pc3,4 cannot be u n d e r s t o o d  without  a knowledge o f t h e s t r u c t u r e and t h e p h y s i c a l p r o p e r t i e s of the magnetosphere.  One of the most i m p o r t a n t  f i n d i n g s i n the past  five  .years which has had profound i n f l u e n c e on m i c r o p u l s a t i o n r e s e a r c h i s the d i s c o v e r y of the s o - c a l l e d 'knee' boundary i n the magnetosphere.  Using w h i s t l e r data, Carpenter  (1963)  deduced t h a t the e q u a t o r i a l e l e c t r o n number d e n s i t y drops a b r u p t l y by two o r d e r s o f magnitude a t a r a d i a l of s e v e r a l e a r t h r a d i i . which was d e s i g n a t e d  distance  T h i s abrupt d e n s i t y d e c r e a s e ,  'knee' by C a r p e n t e r and i s now  also  known as the p l a s m a p a u s e , was l a t e r found t o be a r e g u l a r 1  three-dimensional  1  f e a t u r e of the magnetosphere  1966; Angerami and C a r p e n t e r ,  (Carpenter,  1966).  . The plasmapause d i v i d e s the magnetosphere i n t o two r e g i o n s , namely, the plasmasphere (the i n n e r r e g i o n ) , and the plasmatrough bounded by the magnetopause (See F i g . I . l ) . The east-west asymmetry of the plasmapause conf i g u r a t i o n has been r e p o r t e d by C a r p e n t e r .  I t has been  found t h a t the dimensions as w e l l as the c o n f i g u r a t i o n of the plasmapause depend s t r o n g l y on the p l a n e t a r y magnetic c o n d i t i o n s represented  by the v a l u e of the Kp-index.  g e n e r a l p r o p e r t i e s of the plasmapause as r e p o r t e d C a r p e n t e r are d e s c r i b e d  i n Appendix 1.  by  Carpenter's  d e s c r i p t i o n o f the g e n e r a l p h y s i c a l p r o p e r t i e s of the magnetosphere has p r o f o u n d l y  a f f e c t e d the model t o be  chosen t o i n t e r p r e t o b s e r v a t i o n a l r e s u l t s r e p o r t e d i n this thesis.  The  6  .' ' Both- t h e A l f v e n v e l o c i t y i n t h e and  the  line  estimated  equatorial  fundamental eigen-period  presence of the in  f o r each  o s c i l l a t i o n have been c a l c u l a t e d u s i n g the  e l e c t r o n density d i s t r i b u t i o n that takes  the p r e s e n t  plasmapause.  the  d i s t r i b u t i o n along magnetic f i e l d t o be of the  equatorial  i s assumed  l i n e s of f o r c e i s t a k e n ( n = 1 i s assumed)  l o c a l magnetic f i e l d  of the  f o l l o w i n g Watanabe (1965), W e n t w o r t h ( 1 9 6 5 ) , B r i c e and  others.  Pig.  1.2.  The  Under the  r e s u l t i s s u m m a r i z e d by  to resonance i n the d i f f e r e n t p o r t i o n s of the might expect t h a t  earth (1965),  a g r a p h shown i n  assumption that micropulsations  m a g n e t i c c a v i t y , one  the  electron density  p r o p o r t i o n a l t o a c e r t a i n power n i n t e n s i t y of the  field  i n t o account  A dipole f i e l d  c a l c u l a t i o n , and  region  are  due  Earth's  micropulsations  g e n e r a t e d and/or p r o p a g a t e d i n s i d e each c a v i t y bounded the  A l f v e n v e l o c i t y maxima c o u l d  characterize different  p h y s i c a l p r o p e r t i e s of each of these The  general  regions.  problem of resonances i n a  p l a s m a m a g n e t i z e d by  a dipole f i e l d  is  confined  mathematically  p o n d e r o u s (Dungey, 1954;  C a r o v i l l a n o and  A subset of t h i s g e n e r a l  problem, which c o n s i d e r s  McClay,  s p e c i a l case of a x i s y m m e t r i c o s c i l l a t i o n s has more a t t e n t i o n .  by  I t i s found that t h i s  ment p r o d u c e s a s i g n i f i c a n t d e c o u p l i n g  1965). the  received  symmetry r e q u i r e of the  v e c t o r wave  7  e q u a t i o n i n t o independent  t o r o i d a l and p o l o i d a l modes.  The  t o r o i d a l mode i s r e p r e s e n t e d by t h e a z i m u t h a l component of the p e r t u r b e d v e l o c i t y / and t h e p o l o i d a l mode i s r e p r e s e n t e d by t h e same component o f t h e p e r t u r b e d e l e c t r i c f i e l d .  The  p r i n c i p a l d i f f e r e n c e between t h e two modes i s t h a t the energy o f t h e t o r o i d a l mode i s guided a l o n g t h e f i e l d  line  and so should be s t r o n g l y l a t i t u d e - d e p e n d e n t whereas t h e p o l o i d a l mode s h o u l d n o t .  Many a u t h o r s have t r e a t e d t h e  t o r o i d a l mode under v a r i o u s assumptions  c o n c e r n i n g the  plasma d e n s i t y (Kato and Watanabe, 1956; Obayashl and Jacobs, 1958; Westphal and Jacobs, 196I; R a d o s k i and C a r o v i l l a n o , 1966).  I t i s n o t u n t i l r e c e n t l y , however,  t h a t a t h e o r e t i c a l attempt has been made t o study t h e p o l o i d a l o s c i l l a t i o n i n t h e magnetosphere. I t i s w i d e l y b e l i e v e d t h a t t h e P c 3 range o f p u l s a t i o n i s caused by a s t a n d i n g wave o f m o d i f i e d A l f v e n mode • ( p o l o i d a l o s c i l l a t i o n ) e x i s t i n g between t h e plasmapause and the i o n o s p h e r e .  E x p e r i m e n t a l evidence based on o b s e r v a t i o n s  made a t a l o w - l a t i t u d e s t a t i o n by Hirasawa and Nagata and P u k u n i s h l  (1968)  and Nagata  (1966)  p r o v i d e s support t o t h i s  suggestion. A t h e o r e t i c a l c a l c u l a t i o n has been performed by Radoski  (1967)  where he shows t h a t t h e p o l o i d a l ' w a v e  equation  i s s e p a r a b l e i n . s p h e r i c a l c o o r d i n a t e s under the assumption of  an a x i s y m m e t r i c plasma d e n s i t y ( i . e .  t h e A l f v e n speed  8  increases l i n e a r l y with radial distance) field.  These s i m p l i f y i n g  represent  a reasonable  plasmasphere.  assumptions are considered t o  first  Radoski's  and ambient d i p o l e  approximation  calculation  applicable i n the  shows t h a t t h e z e r o  order fundamental period of p o l o i d a l o s c i l l a t i o n p l a s m a s p h e r e i s 34.2 s e c o n d s w i t h t h e s e c o n d c o r r e c t i o n l e s s than of P c 3 t y p i c a l  i n the  order  one s e c o n d , w h i c h i s t h e mean p e r i o d  o f m i d - and l o w - l a t i t u d e o b s e r v a t i o n s  under  moderate magnetospheric c o n d i t i o n s . An e i g e n o s c i l l a t i o n o f m o d i f i e d a l s o been c o n s i d e r e d simplified suggests  to exist  A l f v e n mode h a s  i n the plasmatrough.  A  t h e o r e t i c a l c o n s i d e r a t i o n made b y T r u s s e l l  this possibility.  (1966)  Indeed, t h e r e s u l t o f T r u s s e l l ' s  calculation not only indicates that periods of the poloidal o s c i l l a t i o n i n t h e p l a s m a t r o u g h a r e i n t h e Pc3,4 range, it  a l s o p r e d i c t s a change o f t h e s e  periods  the degree o f magnetospheric d i s t u r b a n c e sum  o f Kp, i . e . ^ K p .  as a f u n c t i o n o f  represented  T h i s h a s been summarized by a graph  shown i n P i g . 1.3 w h i c h i s t o be c o m p a r e d w i t h observations  reported  experimental  i n Chapter IV (see F i g . IV.2b).  I t has been observed i n t h e present  research that i f  the e x i s t e n c e o f s t a n d i n g p o l o i d a l o s c i l l a t i o n s both  by t h e  s e t up i n  t h e p l a s m a s p h e r e and t h e p l a s m a t r o u g h i s assumed, some  of t h e e x p e r i m e n t a l Ralston  o b s e r v a t i o n s made a t t h e m i d - l a t i t u d e  s t a t i o n may be e x p l a i n e d , n a m e l y , t h e a p p a r e n t  9  d i v e r s i t y o f m o r p h o l o g i c a l p r o p e r t i e s o f P c 3 f r o m one d a y to  another.  A q u a l i t a t i v e d e s c r i p t i o n o f how e a c h o f t h e  f o u r d i f f e r e n t d i u r n a l p a t t e r n s may a p p e a r a s a f u n c t i o n o f the  Kp i n d e x I s p r e s e n t e d i n t h e l a s t  s e c t i o n of Chapter I I I ,  and f u r t h e r c h e c k i n g b y e x p e r i m e n t a l o b s e r v a t i o n a s discussed i n Chapter IV.  The c r u x o f t h e p r e s e n t i n t e r -  p r e t a t i o n i s that Ralston,, which i s l o c a t e d near the plasmapause  under moderate magnetospheric a g i t a t i o n ,  p i c k up m i c r o p u l s a t i o n a c t i v i t y plasmasphere relative  may  o r i g i n a t i n g from the  and/or t h e p l a s m a t r o u g h depending upon t h e  p o s i t i o n of t h e plasmapause.  Two d i f f e r e n t  approaches have been p r o p o s e d i n t h i s  t h e s i s t o l o c a t e the plasmapause,  assuming t h e e x i s t e n c e of  e i g e n o s c i l l a t i o n I n b o t h t h e p l a s m a t r o u g h and t h e p l a s m a sphere.  I n the f i r s t  a p p r o a c h , one may t a k e c o n t i n u o u s  observations over a single  s t a t i o n i n the mid-latitudes.  The movement o f t h e p l a s m a p a u s e  will  be m a n i f e s t e d i n t h e  c h a n g i n g d i m e n s i o n s o f e a c h o r b o t h o f t h e e a r t h ' s two magnetic  resonators, which i n t u r n are represented i n the  changing e i g e n p e r i o d of the ground-observed (Pc3  range).  micropulsation  The movement o f t h e p l a s m a p a u s e  d e p e n d s on t h e  l e v e l o f magnetic d i s t u r b a n c e s i n t h e magnetosphere  as w e l l  as on t h e v a r i a t i o n o f t h e s o l a r w i n d p a r a m e t e r s r e p r e s e n t e d by t h e c h a n g i n g v a l u e o f t h e K^ i n d e x . of  magnetic a c t i v i t y ,  K , boundary  At c e r t a i n  r e p r e s e n t e d by d i f f e r e n t  levels  values of  e f f e c t s may be o b s e r v e d a t R a l s t o n t h a t  will  10  i n d i c a t e the approximate l o c a t i o n of the plasmapause. Kp dependence  of P c 3 observed at R a l s t o n w i l l be  The  studied  i n Chapter I V . The second approach one may t a k e t o l o c a t e the plasmapause i s t o have s i m u l t a n e o u s o b s e r v a t i o n s made over a chosen d i s t r i b u t i o n of s t a t i o n s , a number of which p r e f e r a b l y l i e a l o n g the same m e r i d i a n .  Comparison' of  these s i m u l t a n e o u s r e c o r d s would i n d i c a t e the l a t i t u d e dependence  of P c 3 f r e q u e n c y which i n t u r n would p r o v i d e  i n f o r m a t i o n on the p o s i t i o n of the plasmapause. The second approach i s s u p e r i o r .to the f i r s t , p r o v i d e d the network of s t a t i o n s i s w e l l chosen and the s t a t i o n s are o p e r a t i n g i n an e x a c t l y i d e n t i c a l manner, f o r i t i s p o s s i b l e t o p i n p o i n t more a c c u r a t e l y the l o c a t i o n of the  plasmapause at a g i v e n i n s t a n t of t i m e . I n C h a p t e r V, the l a t i t u d e - d e p e n d e n c e as w e l l as  the  l o c a l time dependence  of P c 3 are s t u d i e d u s i n g the  c l a s s i f i c a t i o n scheme proposed i n Chapter I I I as a g u i d e line.  A network of t h r e e main s t a t i o n s i s chosen f o r  comparison.  These s t a t i o n s are so s i t u a t e d t h a t two of  them, namely Great Whale R i v e r and M c G i l l , l i e c l o s e t o the same geomagnetic m e r i d i a n whereas R a l s t o n and M c G i l l are at about the same geomagnetic l a t i t u d e .  The  telluric  sonagrams p u b l i s h e d i n High L a t i t u d e G e o p h y s i c a l Data by the G e o p h y s i c a l I n s t i t u t e , C o l l e g e , A l a s k a over a p e r i o d from. J a n u a r y t o March 1967  have a l s o been used f o r comparison.  11  The  observational  support  results  thus  f o r the postulated  obtained  provide  model d e s c r i b e d  further  i n the  previous  chapters. A p r e l i m i n a r y study observed in  at Ralston,  has been c a r r i e d  the r e s u l t  of which  o u t on  will  be  Pc4  reported  Chapter V I . In the f i n a l  experiments t h e s i s may  so t h a t  chapter,  we  shall  some o f t h e i d e a s  be i n v e s t i g a t e d .  propose  future  described  i n this  12  F I G - 1.1  THE  MAGNETOSPHERIC  REGIONS  13  FIG. 1 . 2  MAQNETOSPHERIC  EQUATORIAL  ALFVEN  VELOCITIES  fmHz  70 60 50  40 30  20 10  0  5  10  15  20  25  30  35  50~  F I G . 1.3 THEORETICAL ESTIMATION OF DEPENDENCE 0F~PC 2, 3 and 4 PERIOD I N THE PLASMATROUGH ON MAGNETIC A C T I V I T Y (AFTER TRUSSEL,1966)  15 CHAPTER SOURCE  II.1  OF  DATA  II  AND  INSTRUMENTATION  SOURCE OF DATA Data recorded  o n c h a r t s and r e c e n t l y a l s o o n t a p e s  have b e e n made a v a i l a b l e t h r o u g h t h e D e f e n c e R e s e a r c h lishment, field  Pacific.  F o r more t h a n e i g h t y e a r s  cooperative  work h a s been c a r r i e d o u t between t h e R a d i o  Laboratory,  Stanford  U n i v e r s i t y , the P a c i f i c  Estab-  Science  Naval  Laboratory  (now t h e D.R.E.P.) a n d t h e U n i v e r s i t y o f B r i t i s h  Columbia.  One o f t h e m a i n i n t e r e s t s h a s b e e n c o n j u g a t e  point Byrd. was  s t u d i e s a t t h e two s t a t i o n s , G r e a t Whale R i v e r and A third mid-latitude  also established.  identical specific  systems.  station at Ralston,  A l l s t a t i o n s are i n s t a l l e d  Magnetograms r e c o r d e d  days i n the e a r l i e r y e a r s  a v a i l a b l e through the cooperation The Geophysical Alaska  telluric  Alberta with  at McGillf o r  (1963-1965) a r e a l s o o f t h e D.R.E.P.  sonagrams p u b l i s h e d  Data by t h e G e o p h y s i c a l  i n High  Institute,  Latitude  College,  o v e r a p e r i o d f r o m J a n u a r y t o M a r c h 1967 h a s a l s o  been used i n t h i s i n v e s t i g a t i o n . In F i g . I I . l a , p o s i t i o n of the various  a map i s p r o v i d e d stations.  g e o g r a p h i c l a t i t u d e and l o n g i t u d e in  Table I I . 1 .  showing the r e l a t i v e  The g e o m a g n e t i c a n d of each s t a t i o n are l i s t e d  16  :  ... The a v a i l a b l e d a t a on t h e r a p i d v a r i a t i o n o f t h e  e a r t h ' s magnetic f i e l d were r e c o r d e d i n t h r e e o r t h o g o n a l f i e l d components X, Y, and Z a l o n g the g e o g r a p h i c  east-  west, n o r t h - s o u t h and v e r t i c a l d i r e c t i o n s r e s p e c t i v e l y , but  i f comparisons are t o be made among s t a t i o n s , c a r e must  be t a k e n t o account f o r any l o c a l anomaly t h a t may e x i s t . Weaver (1963) and o t h e r s have shown t h a t a c o n d u c t i v i t y d i s c o n t i n u i t y w i l l m a t e r i a l l y a f f e c t the r a t i o of the v e r t i c a l t o h o r i z o n t a l components o f the magnetic  field.  However, s i n c e even d r y e a r t h i s a good r e f l e c t o r as f a r as micropulsation  f r e q u e n c i e s are concerned the magnitude o f  the h o r i z o n t a l components should n o t be g r e a t l y a f f e c t e d by the n e a r n e s s o f a c o n d u c t i v i t y d i s c o n t i n u i t y .  Experimentally,  t h i s has been found t o w i t h i n a t l e a s t a f a c t o r o f two; see for  example C h r i s t o f f e l e t a l (1961) -who show r e s u l t s from  Westham I s l a n d .  The i n t e n s i t y o f the h o r i z o n t a l components  were o n l y s l i g h t l y a f f e c t e d by the c o n t r a s t  i n conductivity.  Lokken (1964) a l s o found t h a t m i c r o p u l s a t i o n s  i n the  v e r t i c a l component, as would be e x p e c t e d , a r e v e r y much reduced i n i n t e n s i t y over Sable  Island.  Throughout t h e c o u r s e o f t h e study t o be r e p o r t e d here t h e r e f o r e ,  o n l y the h o r i z o n t a l X and Y components a r e  used f o r i n v e s t i g a t i o n . any c o n c l u s i o n s  No attempt has been made t o deduce  that include  t h e Z component.  17  A l s o , s i n c e t h e X and Y c o m p o n e n t s a r e v e r y we  have p r o c e s s e d  f r o m R a l s t o n a l l o f t h e 1967  similar,  magnetic  tape  d a t a f o r t h e X component w h e r e a s t a p e r e c o r d e d d a t a f o r 3 m o n t h s o n l y ( F e b r u a r y , M a r c h , and processed  f o r the Y  Only  A u g u s t 1967)  have been  component.  t h e X component r e c o r d e d on  tape i s of  sufficiently  l o w n o i s e t o s i g n a l r a t i o a t G r e a t Whale i n t h e P c 2 , 4 frequency  range,  and A u g u s t 1967)  and  3,  d a t a f o r t h r e e months ( F e b r u a r y ,  have been  and March,  processed.  M i c r o p u l s a t i o n d a t a r e c o r d e d c o n t i n u o u s l y on c h a r t a v a i l a b l e f r o m R a l s t o n , B y r d and components.  Normally  G r e a t Whale i n b o t h X and  tion.  used,  Y  t h e y were r e c o r d e d w i t h a c h a r t speed  o f 6 i n c h / h o u r , but o c c a s i o n a l l y , a h i g h c h a r t speed o f i n c h / m i n was  are  p r o v i d i n g a much h i g h e r f r e q u e n c y  3/4  resolu-  H i g h - s p e e d c h a r t - r e c o r d e d magnetograms a r e a l s o a v a i l -  a b l e f r o m M c G i l l and Westham I s l a n d i n b o t h X and Y for specific Of  time  components  intervals.  t h e v a s t amount o f c h a r t r e c o r d e d d a t a  a synoptic examination  o n l y has  been t a k e n .  The  available, data  are  so s e l e c t e d t h a t o n l y t h o s e a v a i l a b l e s i m u l t a n e o u s l y f r o m maximum number o f s t a t i o n s a r e u s e d .  I n T a b l e II.2,  a  the  d i f f e r e n t forms of d a t a from v a r i o u s s t a t i o n s used i n the p r e s e n t i n v e s t i g a t i o n have been t a b u l a t e d . X,  Y,  and XY  r e p r e s e n t the f i e l d  p a r t i c u l a r time i n t e r v a l .  The  designations  components examined i n t h a t  XY means X and  Y.  TABLE I I . 1 THE  Station  —  Byrd  LOCATION AND MAGNETIC ELEMENTS OF STATIONS FROM WHICH DATA WAS MADE AVAILABLE  Geographic  Geo magnet i c  Left (N) Long (W)  (BY) -80°00'  119°30'  Lat (N) -Long (E)  -70°.6  336°.3  I n c l . of Field  Line  - 74°.8  Average T o t a l  HJ_  Field  _D_  ZJ_  15,330  68°28»  57,400  9,450  21°39'  5^,700  Great Whale River(GW)  55°l6'  77 47'  66 .6  347°.4  81°.1  College (Co)  64°'52'  147°50'  64-6  256°.5  77°. 0  12,610  -28°07*  55,227  Ralston (RA)  51 12'  ^ lll 07  53°.8  305 .5  72°.0  17,045  19 4 5 '  52 , 466  -67°.1  22,500  32°00»  53,084  n  0  n  o  ,  Eights (EI)  -75 34»  77 10'  (MG)  45°32'  73 09  Westham Island (WI)  49°06»  123°11»  -63°.8  355°.3  McGill o  ,  57°.0  354 .3  74°.9  15,220  15°20»  56,170  54°.7  292°.9  71°.0  18., 860  22°.35'  53 , 2 05  20 TABLE SELECTED ' IN  Form o f Data  THE  II.2 DATA  PRESENT  USED  INVESTIGATION  S t a t i o n  Date.  GW  BY  1967 J a n  X  Feb  X  XY  Mar  X  XY  Apr'  X  Tape (FM)  May-  X  0.025 i n . / s e c  June  X  July  X  Aug  -  to  -Sp-i  3/4  in/min  03  x: 0 w W <  0)  Sept  X  Oct  X  Nov  X  Dec  X XY  XY  Aug 14-20  XY  XY  1966 A u g 15-20 Nov 16-18  XY  XY  XY  Y  Y  Y  1965 J u n 14-25 Sep 14-25 Dec 15-22 1964 J a n 15-20 A p r 15-20  XY  XY  XY  XY  XY  XY  XY  XY  XY  XY  XY  Y  Y  Y  Y  Y  Y  1967 J a n  XY  XY  Y Y  EI  s  1967 F e b 14-20  Y  H •r-i  Feb  1-13  XY  XY  Feb 22-30  XY  XY  Mar  XY  XY  Oct  XY  XY  Nov Dec  XY  XY  XY  XY  6 in/hour  WI  XY  Este  c  X  MG  RA  s  XY  F  21  Form o f Data  S t a t i 0 n s  Date  GW  MG  WI  Y  Y  Y  Feb  Y  . Y  Y  Mar  Y  Y  3 cm/min  Apr  Y  May  Y  June  Y  July  Y  Aug  2 cm/min  RA  .1967 J a n  Helicorder Chart  L a C o u r Type. Magnetogram  BY  1965  Y  Y  Sept  Y  Oct  Y  Nov  • Y  Dec  Y  J u n 14- 25  HD  Sep 14- 25  HD  Dec  HD  15- 22  EI  22  II.2  RECORDING AND REPRODUCING SYSTEM The  r a p i d v a r i a t i o n o f t h e geomagnetic f i e l d has  been r e s o l v e d i n t o t h r e e o r t h o g o n a l purpose o f d e t e c t i o n .  components f o r t h e  The d e t e c t i n g equipment i n t h e  h o r i z o n t a l axes (X i n t h e geographic n o r t h - s o u t h  and Y i n  the e a s t - w e s t d i r e c t i o n s ) c o n s i s t e d o f mumetal cored solenoids.  S i g n a l s r e c e i v e d by these c o i l s were f e d t o  r e c o r d e r s t h r o u g h d.c. chopper a m p l i f i e r s . Two t y p e s o f d a t a r e c o r d e r s were used.  One i s  the E s t e r l i n e Angus c h a r t r e c o r d e r , w i t h a c h a r t speed o f 6 i n c h p e r hour o r w i t h a h i g h e r speed o f 3 / 4 i n c h p e r minute.  F o r a n a l y s i s , t h e h i g h e r speed was used f o r P c 2 ,  3 and 4 m i c r o p u l s a t i o n s i g n a l s and t h e slower Pc3,  4 and 5 s i g n a l s .  speed f o r  The h i g h e r speed was r e q u i r e d t o  r e s o l v e P c 2 w h i l e the l o n g p e r i o d P c 5 c o u l d b e s t be observed at t h e slower  speeds.  Data may a l s o be r e c o r d e d  on magnetic t a p e s .  The  r e c o r d i n g tape speed i s 0 . 0 2 5 i n c h p e r second ( 7 - 5 f t . p e r hour).  T h i s p r o v i d e 1 0 days o f c o n t i n u o u s  r e c o r d i n g on  lSOO f e e t of 1 m i l magnetic tape ( 7 i n c h r e e l s , 1/4 i n c h wide tape).'  I n o r d e r t o i d e n t i f y e v e n t s recorded  on t a p e s ,  simultaneous  r e c o r d i n g s were made on h e l i c o r d e r c h a r t s  o p e r a t i n g w i t h a c h a r t speed of 3 cm p e r min. The  frequency  domain o f i n t e r e s t d e f i n e d by t h e  D.R.E.P. group ( E n g l i s h e t a l , 1 9 6 l ) who were r e s p o n s i b l e f o r the experimental  o p e r a t i o n s , has an upper  frequency  23  limit  o f 100  Hz and a l o w e r l i m i t  response c u r v e f o r the equipment b y E n g l i s h e t a l (1961),  o f 0.01  Hz.  o f t h e D.R.E.P. g r o u p ,  s y s t e m i s shown i n P i g . I I . 2 b ,  1964;  a detailed  recording  description  R e s e a r c h B o a r d o f Canada  Shand e t a l , 1959; The  Gibb,  (weir,  1966;  1968).  a frequency m u l t i p l i c a t i o n of  r e c o r d b a n d w i d t h i s 0 t o 4.0 Hz.  Hz and  the  inch  150,  t h e r e f o r e 10 d a y s o f d a t a c a n be p l a y e d b a c k i n 1.6  b a n d w i d t h i s 0 t o 600  by  Lokken  r e p r o d u c t i o n s p e e d f o r t h e t a p e i s 3-3/4  per second, g i v i n g  The  of  be f o u n d i n t h e T e c h n i c a l Memoranda p u b l i s h e d  the Defence  given  i s shown i n P i g . I I . 2 a .  A b l o c k diagram of the m i c r o p u l s a t i o n  w h i c h may  The f r e q u e n c y -  hours.  reproduction  so  DETECTOR F I L T E R 'fit AJAPUFIE.R FORT  OOl  CHURCHU_V_,|V\AN.  PIG.  II.2a  M O . I-WLS O C T . 2 . , 1^60  l-O  O'l  Fceouervcy  NO. IS  Cycles  per s e c o n d  FREQUENCY RESPONSE OF F . M. RECORDING oYSTEM  IO  Signal Monitor  -i  I  Calibration  \A/V  Current  rI  Generator  X  Input  Chopper  Filter  Amplifier  Input Filter  Slow 1  o  Speed  Slow Sp Tape  F. M. R e c o r d U  n  i  Trock 1  X  1  u a> ; 1  £ 9-  o  Y  2  7 ^  2  3 3.  >  Z  4  6 I  6  Single Channel Reproduce Monitor  FIG. II.2b  MICROPULSATION RECORDING  Unit  SYSTEM  6 44  »  3  "  4  26  II.3  TAPE ANALYSING  SYSTEM  In order t o feed the output of the reproducing u n i t (which has a l r e a d y been m u l t i p l i e d  b y 150  times the frequency  of the s i n g a l ) i n t o a sonagraph  f o r s p e c t r a l a n a l y s i s of the  Pc3 f r e q u e n c y range,  s i g n a l must be  the output  speeded t o s u i t t h e d e s i g n o f t h e sonagraph. this,  To a c h i e v e  the output o f t h e r e p r o d u c i n g u n i t has been r e - r e c o r d e d  by an e i g h t - c h a n n e l S a n b o r n t a p e speed  o f 15/16  t o 313  Hz).  i n c h p e r second The r e c o r d e d  a h i g h e r speed  recorder with a recording  ( r e c o r d i n g bandwidth  o f 60 i n c h p e r s e c o n d  (reproduce  t o 0.1  s p e e d e d up t o 96 t o 96O sonagraph. Kay E l e c t r i c  bandwidth  speed-up f a c t o r o f  x 64, o r 96OO, h a s b e e n a c h i e v e d .  s i g n a l i n t h e 0.01  i s d.c.  s i g n a l i s then p l a y e d back w i t h  i s d . c . t o 20 K H z ) , t h u s a r e s u l t a n t 150  further  Hz. f r e q u e n c y  Thus, a m i c r o p u l s a t i o n range  h a s now b e e n  Hz, r e a d y t o be p r o c e s s e d b y t h e  The s p e c i f i c a t i o n and t e c h n i c a l d a t a f o r t h e sonagraph  are t a b u l a t e d i n Appendix  2for  reference. The v i s u a l r e c o r d s w h i c h  c o n t a i n the a n a l y s i s of  t h e r e c o r d e d m i c r o p u l s a t i o n waves a r e made on current sensitive,  f a c s i m i l e - t y p e paper.  non-photographic,  The p a p e r  i s mounted  on a drum whose a x i s i s t h e same a s t h e t u r n t a b l e on whose p e r i p h e r y the continuous magnetic  recording f i l m i s deposited.  The a r r a n g e m e n t p r o v i d e s a u t o m a t i c  time  synchronization.  r e c o r d i s t r a c e d by a s t y l u s which  a d v a n c e s u p w a r d , and a t  t h e same t i m e c h a n g e s t h e a p p a r e n t  center frequency of the  The  2 7  a n a l y z i n g band pass f i l t e r . to  A high-frequency current applied  the s t y l u s i s v a r i e d i n a m p l i t u d e i n p r o p o r t i o n t o the  amount o f energy passed by t h e bandpass f i l t e r .  The f i r s t  type o f r e c o r d o b t a i n a b l e d i s p l a y s time on t h e a b s c i s s a , f r e q u e n c y on t h e o r d i n a t e , and i n t e n s i t y as s h a d i n g between gray and b l a c k . The second type of r e c o r d d i s p l a y s i n t e n s i t y i n db v s . f r e q u e n c y a t as many as s i x s e l e c t e d t i m e s .  This  d i s p l a y has a dynamic range i n i n t e n s i t y of 35 db. The t h i r d type of r e c o r d d i s p l a y s average vs.  available  amplitude  time w i t h i n a dynamic range o f 3^ db maximum. Only t h e f i r s t  type o f r e c o r d , i . e . t h e f r e q u e n c y -  time d i s p l a y , however, has been found u s e f u l i n our p r e s e n t investigation.  I n a d d i t i o n , a Kay E l e c t r i c c o n t o u r u n i t  has been used t o produce c o n t o u r e d sonagrams which a r e u s e f u l i n l o c a t i n g the mid-band f r e q u e n c y o f a g i v e n s i g n a l . A s c a l e expander i s a l s o a v a i l a b l e t o expand t h e f r e q u e n c y s c a l e so t h a t , c o u p l e d w i t h a c o r r e c t c h o i c e of r e c o r d i n g speed, any p o r t i o n of a g i v e n spectrogram may be expanded to  show a f i n e r  detail.  The t e l l u r i c  sonagrams p u b l i s h e d i n High L a t i t u d e  G e o p h y s i c a l Data by t h e G e o p h y s i c a l I n s t i t u t e , C o l l e g e , A l a s k a and used i n t h i s t h e s i s f o r comparison  purposes i s  a continuous frequency-time d i s p l a y of t e l l u r i c current a c t i v i t y i n the p e r i o d range o f 9 t o 500 sec.  The t e l l u r i c  system has t h e advantage of l a r g e r low f r e q u e n c y  response  28  t h a n an i n d u c t i o n l o o p s y s t e m and a b e t t e r ratio  because  of the m i l l i v o l t s  a v a i l a b l e from the  e l e c t r o d e s i n comparison w i t h the m i c r o v o l t induction  amplifier  s i g n a l of the  i s a Medistor microvoltmeter set at  r a n g e and l o g a r i t h m i c  scale.  The  logarithmic  makes i t p o s s i b l e t o accommodate t h e w i d e d y n a m i c activity  telluric  loop.  The 10 mv  s i g n a l to noise  response  range  which o c c u r s a t C o l l e g e i n the f r e q u e n c y range  investigation.  Thus w i t h c o n s t a n t g a i n s e t t i n g s the  a m p l i t u d e Pc3 daytime a c t i v i t y on t h e s o n a g r a m s , t a t i o n due The  c a n be b r o u g h t o u t  hour.  under  low  clearly  and w i t h no o v e r l o a d i n g o f t h e i n s t r u m e n -  to the powerful n i g h t t i m e P i  activity.  t a p e r e c o r d e r i s a K n i g h t 4000A d i r e c t  record  i n s t r u m e n t w h i c h h a s b e e n m o d i f i e d t o r e c o r d a t 1-1/6 per  of  inch  The f r e q u e n c y r e s p o n s e o f t h e p l a y b a c k a m p l i f i e r  and V i b r a l y z e r  a r e shaped  such t h a t average a c t i v i t y  at the  b o t t o m o f s o n a g r a m i s n o t t o o b l a c k and a v e r a g e a c t i v i t y the  top i s not too f a i n t .  was  made t o i n c r e a s e m o n o t o n i c a l l y t o w a r d h i g h e r f r e q u e n c i e s .  If  a flat  To a c c o m p l i s h t h i s ,  the  at  r e s p o n s e had b e e n u s e d , t h e u p p e r p a r t o f t h e  s o n a g r a m s w o u l d u s u a l l y be b l a n k when a r e a s o n a b l e was  response  p r e s e n t at the bottom.  not s u f f i c i e n t  The  to s i g n i f i c a n t l y  level  departure from f l a t n e s s i s distort  the Pc3-5  activity.  29  CHAPTER SUBCLASSIFICATION VARIATION  III.l  OF  Pc3  Pc3  IN  MID-LATITUDE-DIURNAL  FREQUENCY  AT  RALSTON  INTRODUCTION Recently,  data  OF  III  that there  v a r i o u s a u t h o r s h a v e shown f r o m i s a d e f i n i t e connection  o f c o n t i n u o u s p u l s a t i o n ( P c 2,  3,  and  4)  satellite  between the and  the changes  m a g n e t o s p h e r i c d i m e n s i o n ( B o l s h a k o v a and  Troitskaya,  B o l s h a k o v a , 1965a; N a g a t a e t a l , 1 9 6 6 ) .  The  p u l s a t i o n s may  of the  be  the p e r i o d  as  a new  place  i s indeed  p h y s i c a l c o n d i t i o n of the  o u s l y w i t h a most e c o n o m i c  of  continu-  characteristic  event takes  micropulsation  beyond, m i c r o p u l s a t i o n  1964;  1965a; N a g a t a e t a l ,  a Pc3  Since  o f a Pc3  t i o n o f the g e n e r a l and  to serve  s o l a r wind (Bolshakova,  T r o i t s k a y a , 1967). if  able  research  a  1966;  every  manifesta-  us  continu-  exosphere.  R e s e a r c h i n the d i u r n a l b e h a v i o u r of the  continuous  m i c r o p u l s a t i o n p e r i o d i s a t o p i c w h i c h i s n e a r l y as o l d the  subject  systematic  itself.  E.R.R. H o l m b e r g ( 1 9 5 1 ,  c h a n g e o f Pc3  and  Pc4  periods  known s c a t t e r d i a g r a m o f p e r i o d a g a i n s t by  an  1927.  i n d u c t i o n loop Since  day,  magnetosphere  could provide  'window' t o t h e  of  same a u t h o r s  have i n d i c a t e d a l s o t h a t the v a r i a t i o n i n p e r i o d ous  period  and  1953)  noticed  produced the  time u s i n g  a t E s k d a l e m u i r as e a r l y as  t h e n many w o r k e r s h a v e r e p o r t e d  as  1926  data  the wellobtained  and  r e s u l t s of  their  30  o b s e r v a t i o n s , and y e t t h i s p a r t i c u l a r matter from  of c o n t r o v e r s y even today.  s u b j e c t remains  Many a u t h o r s  a  concluded  s c a l i n g magnetograms t h a t t h e f r e q u e n c y o f P c 3 behaves  as a U - t y p e  ( i n v e r t e d U-type i n p e r i o d ) d i u r n a l  ( K a t o and S a i t o ,  1959; Y a n a g i h a r a ,  variation  1959; Pope e t a l , 1962;  H o l m b e r g , 1953), t h a t i s t o s a y t h e f r e q u e n c y o f P c 3 i s l o w e r i n the a f t e r n o o n than t h a t i n the morning.  More r e c e n t  o b s e r v a t i o n s made b y s e v e r a l r e s e a r c h e r s u s i n g d a t a on c h a r t s a s w e l l a s o n s l o w s p e e d m a g n e t i c the c o n t r a r y .  U s i n g s l o w speed m a g n e t i c  at Kakioka F i e l d latitude),  S t a t i o n i n Japan  Hirasawa  frequency of P c 3 and  tapes  recorded demonstrates  tape data  recorded  (26.0° i n g e o m a g n e t i c  and N a g a t a (1966) r e p o r t e d t h a t t h e  appears  t o be h i g h e r e a r l y i n t h e m o r n i n g  then decreases t o the lowest p o i n t l a t e i n the afternoon.  T h i s r e p o r t agrees w i t h the r e s u l t (1961) u s i n g a l s o from Hobart  ( (p = 5 2 ° ) ,  and T o w n s v i l l e ( 0 Other observed different  slow speed  tape  shown e a r l i e r by D u n c a n r e c o r d e d d a t a and c h a r t s  Camden ( 6 = 4 3 ° ) , A d e l a i d e  = 29°)  a similar trend at Lerwick  At E s k d a l e m u i r ,  = 45°)  i n Australia.  a u t h o r s , n o t i c e a b l y S t u a r t and U s h e r  at Eskdalemuir  (6  (1966)  ( <ji = 6 2 . 6 ° ) , b u t  { (j) = 5 8 . 5 ° )  and H a r t l a n d ( $  =  55.1°).  the d i u r n a l v a r i a t i o n of frequency i s very  s l i g h t w h e r e a s an i n v e r t e d U - t y p e o f d i u r n a l v a r i a t i o n i n frequency i s apparent (1968) a l s o f o u n d  at Hartland.  N a g a t a and F u k u n i s h i  i n v e r t e d U-type d i u r n a l v a r i a t i o n i n  frequency at Kakioka,  Japan.  31  Each o f the above mentioned I n f r e q u e n c y has  types of d i u r n a l  b e e n i d e n t i f i e d a t R a l s t o n ( C) =  Some o c c u r more f r e q u e n t l y t h a n o t h e r s . t o be t h e l e a s t f r e q u e n t . 1967  o n l y two  Out  t h e r e f o r e be  58.8°).  U-type i s found  of the d a t a under study i n  s u c h c a s e s were f o u n d ,  under i r r e g u l a r magnetospheric  The  variation  and  these occurred only  conditions.  The  U-type  t a k e n as an e x c e p t i o n a l c a s e r a t h e r t h a n  may a  p e r s i s t e n t phenomenon. On  t h e o t h e r h a n d numerous e x a m p l e s w e r e f o u n d  having  diurnal  v a r i a t i o n r e s e m b l i n g t h a t r e p o r t e d by H i r a s a w a  Nagata,  D u n c a n , S t u a r t and U s h e r ,  Furthermore,  and  and N a g a t a and F u k u n i s h i .  t h e t y p e s r e p o r t e d by t h e s e a u t h o r s may  be  shown t o be p a r t i c u l a r c a s e s o f an e n l a r g e d c l a s s i f i c a t i o n scheme ( o r s u b c l a s s i f i c a t i o n scheme) t h a t we propose  are about  i n t h i s chapter. S c r u t i n y o f d i s p l a y s o f sonagrams (dynamic  p r o c e s s e d from slow speed suggests of  to  spectra)  recorded data recorded at Ralston  that there are f o u r basic types of d i u r n a l  frequency apparent  under steady magnetospheric  variation  conditions.  The  m a j o r i t y o f e v e n t s u n d e r s t u d y c o u l d be c l a s s i f i e d i n t o  one  o f , or the combination o f , these f o u r b a s i c types.  however, does not Imply but  the e x c e p t i o n w i l l  e x c e p t i o n s may  r a r e l y occur.  not take p l a c e ,  Moreover,  these  be shown t o t a k e p l a c e o n l y u n d e r  changing magnetospheric index.  t h a t e x c e p t i o n s may  c o n d i t i o n s r e p r e s e n t e d by  An i n v e r s e r e l a t i o n b e t w e e n K  and  This,  rapidly the  the r a d i u s o f  the  32  m a g n e t o s p h e r e was d o c u m e n t e d  by C a h i l l  Some o f t h e e x c e p t i o n a l c a s e s w i l l Section III.6.  and Amazeen  (I963).  be p r e s e n t e d i n  I n the f o l l o w i n g s e c t i o n s the f o u r proposed  s u b - c a t e g o r i e s of Pc3 c o n t i n u o u s p u l s a t i o n w i l l i n d e t a i l w i t h examples g i v e n wherever p o s s i b l e .  be  described  III.2  M U L T I - B A N D S T R U C T U R E D CONTINUOUS P U L S A T I O N One  our  the  most  pulsation  frequency.  three  defining  i s the  b a n d s may  of B e r k e l e y  of  be  at Ralston.  unusual  a brief  the  resolution some t i m e  reveal  that  indicates  identified  (Jacobs e t  of  waves range  double  magnetograms has  when t h e  periodicity.  But  in  1967.  identified  slow Each last  speed of  these  Pc3  recorded  multi-band  f o r at l e a s t  three  are  for •  (3/4  within  misleading.  further  structured tape  bands sufficient  analysis  I t i s rather fortunate that a  the  not  only for  F u r t h e r , the  each other  t o be  drawn u n t i l  1967).  inch  at m i d - l a t i t u d e s t a t i o n s  available.  of  occur  to provide  may  out  the  been e v i d e n t t o us  Fig. III.2a).  of multi-band  or  1964)  frequency  conclusions  In t o t a l  within  r a p i d - r u n magnetograms  o f t e n proved be  structure  s u b - b a n d s may  they usually  I t has  superimposing (see  of  t h a t two  a l ,  frequency  c h a r t speed) o b t a i n e d  two  frequency  Or,  them.  scrutiny  often identify the  Pc3  Rather  time.  justifies  m i c r o p u l s a t i o n (Mainstone,  distinct  of  that  subclassification  o r d i n a r y sonagraph f a i l s  to  per minute  of  these  interval  overlap,  o f t e n be  resolution  Occurrence  or  evidence  b o u n d a r y ' o f Pc3  the  findings  existence of multi-band  Experimental  frequency  framework  may  interesting  proposal for reclassification  continuous in  of  evidence  has data  hour.s.  Pc3  by  scaling  No  definite  of  13  days  identified  obtained  structured  the  becomes  sample been  periods  Pc3  at  Ralston  events  3 4  In Table I I I . l ,  we h a v e l i s t e d  a l l the days o f h i g h  q u a l i t y m u l t i - b a n d s t r u c t u r e d P c 3 a t R a l s t o n i n 1967. have l i s t e d  a l s o the mid-frequency  We  o f each band f o r c o m p a r i s o n .  W i t h an o n l y e x c e p t i o n o f f ^ w h i c h i s i n t h e P c 4 r a n g e , o t h e r t h r e e bands f ,  and f 4 a r e i n s i d e t h e b o u n d a r y  2  P c 3 d e f i n e d by t h e B e r k e l e y r e s o l u t i o n . the mid-frequency  the of  In order to l o c a t e  o f each i n d i v i d u a l sub-band  accurately,  c o n t o u r e d s o n a g r a m s a r e made w h i c h h a v e b e e n f o u n d t o be most efficient.  We h a v e a l s o l i s t e d  the time i n t e r v a l s d u r i n g  w h i c h m u l t i - b a n d s t r u c t u r e h a s b e e n o b s e r v e d on e a c h o f t h e s e days.  I t i s e v i d e n t from Table I I I . l  that the multi-band  e f f e c t i s s t r o n g e s t around o r j u s t a f t e r l o c a l noon. on t h e d a y s o f m o d e r a t e l y d i s t u r b e d m a g n e t i c we  it  conditions  f i n d s t r o n g m u l t i - b a n d c h a r a c t e r i s t i c s i n the  ( n o t i c e a b l y on November 24, December 6,  1,  Only  morning  and 8,  i s a g a i n on t h e s e m o d e r a t e l y d i s t u r b e d d a y s  do  1967),  that  and  the  f o u r t h b a n d fjj. becomes n o t i c e a b l e . The  a s s o c i a t i o n of Pc4 w i t h the o c c u r r e n c e of m u l t i -  b a n d P c 3 s h o u l d n o t be t a k e n as p u r e l y I n c i d e n t a l . discussion w i l l  be g i v e n i n t h e l a t e r  I n F i g . I I I . 2 b one  Further  sections.  o f t h e most d e m o n s t r a t i v e e x a m p l e s  o f m u l t i - b a n d s t r u c t u r e d P c 3 i s shown.  The m u l t i - b a n d  s t r u c t u r e i s o n l y v a g u e l y seen e a r l i e r i n t h e day.  The  f r e q u e n c y o f a l l b a n d s d e c r e a s e s a s t h e day p r o c e e d s the a f t e r n o o n . o b s e r v e d a t 1100  There L.T.  I s an enhancement o f P c 3 The  towards  activity  enhancement o f b o t h P c 3  bands  35  TABLE CHARACTERISTICS  OF  PULSATION  Date  III.l  CLEAR AT  RALSTON  Mid _  M i d f„ M i d f  f]  MULTI-BAND  0  CONTINUOUS  I N 196?  M i d f,j  Time o f Occurrence  Maximum Intensity 11 - 12 L T  '5  22  0.010  0.025  0.040  O.065?  10 - 12 L T  Feb 11  19  0.010  0.022  0.038  --  Daytime  Noon  Feb 12  4  0.010  0.022  0.035  —  8 - 16 L T  Noon  3  15  0.010  0.020  0.030  J u l 12  17  0.012  0.025  0.035  -— >  Aug  23  10  o.olo  0.025  0.040  Sep  3  12  0.012  0.025  0.040  Sep  4  13  0.012  0.025  0.035  Oct 13  17  0.010  0.025  O.O38  Oct 23  15  0.008  0.020  0.030  Nov 16  17  0.015  0.025  Nov 23  16  0.010  Nov 24  27  Dec  4  Dec  Feb  Mar  Daytime  15  10 - 16 LT  - 16 LT 13 LT  Daytime  12  - 14 LT  --  Daytime  15  - 18 LT  —  4 - 21 L T  16  - 19 L T  Daytime  11 - 16 LT  —  Daytime  12  - 14 LT  O.O38  O.OoO  5 - 18 L T  9  13 L T  0.028  0.045  0.070?  Daytime  13  - 15 LT  0.010  0.025  0.040  0.070  5 - 17 L T  14  0.010  0.022  O.O38  —  6 - 21 L T  12  - 14 L T  6  23  0.015  0.030  0.045  0.070  5 - 19 L T  10  - 17 L T  Dec  7  27  0.010  0.028  0.042  0.065  6 - 18 L T  Dec  8  31  0.010  0.025  0.040  0.070  4 - 16 L T  9 - 15 LT 7 - 8 LT 13 - 14 LT  Dec 12  12  0.008  0.020  0.035  0.011  0.024  O.O38  Average  --  8 - 18 L T  9 - 11 L T  17  - 18 LT  36  takes place simultaneously. Pc4  This i s d i f f e r e n t from  the  b a n d whose i n t e n s i t y h a s b e e n e n h a n c e d e a r l i e r i n t h e  morning. three  Maximum i n t e n s i t y t a k e s p l a c e a r o u n d n o o n f o r a l l  bands. N o t i c e a l s o i n t h i s example the i r r e g u l a r p u l s a t i o n  P12  occurring just before The  and  a f t e r the l o c a l  m a j o r i t y of multi-band  noon o r e a r l y i n the a f t e r n o o n . o f Pc3  i s e i t h e r constant  The  i n c r e a s i n g frequency i n Fig.III.2c band Pc3 and  and  with constant frequency  the case  of multi-band  o c c u r r i n g i n the  has been d e m o n s t r a t e d .  one  index.  1500  L.T.  d i s p l a y an examples,  the case  o c c u r r i n g i n the  multi-  afternoon,  e x a m p l e o f d i s t i n c t 4 band s t r u c t u r e  But  I t i s i n t e r e s t i n g to note the spectrogram  general  the magnetic a c t i v i t y  takes  steady value of  the  spike-like discrete  w h i c h i s most a p p a r e n t  after  T h i s i s c o n t r a r y to the g e n e r a l l y continuous  d i f f u s e d a p p e a r a n c e , s u c h as o c c u r r e d on F e b r u a r y Fig.III.2c.  of  shown  with i n c r e a s i n g frequency  s t e a d i l y as i n d i c a t e d by t h e  appearance of the  morning  T h i s o c c u r s on a day when t h e  disturbance l e v e l i s high. place f a i r l y  Pc3  Two  The  morning.  In Fig.III.2e,  Kp  illustrate  types  This i s different  observed  t r e n d toward noon.  around  of these  i n the. m o r n i n g .  those  and F i g . I I I . 2 d ,  are observed  frequency  or decreasing.  from the t y p e s t h a t are observed type occurs o n l y r a r e l y ,  events  midnight.  12,  and 1967,  J  1  1950  1  L  I  l  I  I  I  i  u.  1955  FIG III2a September 18.1965 M U L T I - P E R I O D I C I T Y  I  OF  Pc3  38  U.T. L.T.  6  8  23 1  i  10 12 14 16 18 I i I • I • 7 9 11 TVI»E e «S S O N A G R A M &  KAY ELBCTIUC CO.  20 22 2 4 6 13 15 17 19 21 23 PINE BROOK. N. J.  604020-  FIG lll.2b RALSTON Y 11 FEB 67 .MULTI-BAND P c 3 WITH DECREASING FREQUENCY FROM DAWN TO DUSK  39  FIG 111.2c RALSTON Y 12 FEB67 M U L T I - B A N D  Pc3 WITH C O N S T A N T  F R E Q U E N C Y  40  FIG lll.2d RALSTON X  15 N0V67  MULTI-BAND Pc3 I N THE EARLY MORNING  41  FIG lll.2e RALSTON X  6 DEC 67  4 BANDS STRUCTURED Pc3,4  42  III.3  NORMAL TYPE WITH MORNING AND AFTERNOON SEPARATION V e r y o f t e n , Pc3 o b s e r v e d  differently evening.  i n the morning  behaves  from t h a t observed i n t h e a f t e r n o o n o r i n t h e  The m o r n i n g  t y p e Pc3 i s u s u a l l y o f l o w e r  frequency  than i t s counterpart i n the afternoon. The m o r n i n g daily  t y p e Pc3 b e h a v e s a s a n i n v e r t e d  U-type  v a r i a t i o n i n f r e q u e n c y w i t h maximum f r e q u e n c y  o c c u r r i n g around  0600 L.T.  This t r a i n u s u a l l y begins  0200 o r 0300 L.T. w i t h l o w f r e q u e n c y w h i c h w o u l d I n c r e a s e towards  dawn.  around  then  A f t e r g o i n g t h r o u g h t h e maximum  f r e q u e n c y n e a r dawn, t h e f r e q u e n c y b e g i n s t o t a k e a downward trend u n t i l  I t reaches  the lowest p o i n t e a r l y i n the a f t e r -  noon. T o w a r d s noon, a new t r a i n b e g i n s t o t a k e p l a c e  which  i s o f h i g h e r f r e q u e n c y t h a n t h e one t h a t e x i s t e d i n t h e morning.  Sudden enhancement o f a c t i v i t y o f t h i s new t r a i n  o c c u r s e a r l y i n t h e a f t e r n o o n and then i t s frequency shes r a p i d l y toward dusk (lbOO L . T . ) .  dimini-  T h i s I s demonstrated  p r o f o u n d l y b y a n e x a m p l e shown I n F i g . I I I . 3 a . The  boundary between t h e morning  and t h e a f t e r n o o n  type i s u s u a l l y w e l l d e f i n e d .  However t h e r e a r e o c c a s i o n s  when t h e b o u n d a r y i s d i f f i c u l t  to locate.  T h i s h a p p e n s when  t h e t w o bands o v e r l a p e a c h o t h e r a t t h e b o u n d a r y . T h e r e i s s t r o n g Kp d e p e n d e n c e o n t h e o c c u r r e n c e of  t h e boundary between t h e morning  time  and the afternoon type  43  Pc3.  Under m o d e r a t e l y d i s t u r b e d c o n d i t i o n s c o r r e s p o n d i n g t o  Kp =  3—*4,  morning.  t h e boundary e f f e c t t a k e s p l a c e e a r l i e r i n the  On t h e o t h e r hand, when the magnetic  condition i s  r e a s o n a b l y q u i e t ( K p ^ 0 -* 2 ) , the boundary e f f e c t  takes  place l a t e r i n the afternoon. In P i g . I I I . 3 b an example i s shown where t h e a f t e r noon type o f P c 3 b e g i n s i n the morning. l e v e l o f magnetic say)..  T h i s o c c u r s when the  d i s t u r b a n c e i s r e a s o n a b l y h i g h ( ^ K p > 25  I t s f r e q u e n c y t h e n d e c r e a s e s as t h e day proceeds  towards t h e a f t e r n o o n .  The morning type o f P c 3 i s o n l y  v a g u e l y r e c o g n i z a b l e , and the s e p a r a t i o n between t h e morning type Pc3 and Pc4 i s n o t t o o c l e a r .  I t i s t h i s type o f  d i u r n a l v a r i a t i o n o f f r e q u e n c y t h a t Hlrasawa (1966)  and Nagata  r e p o r t e d from K a k i o k a , Japan (see P i g . I I I . l ) .  the morning type o f P c 3 observed  Because  at h i g h and m i d - l a t i t u d e s  become v e r y weak a t t h e lower l a t i t u d e , o b s e r v e r s a t lowl a t i t u d e s t a t i o n s would tend t o average  out t h e d i f f e r e n c e  between t h i s type o f P c 3 w i t h the much s t r o n g e r s i g n a l o f Pc4.  Vie s h a l l l e a v e f u r t h e r d i s c u s s i o n o f t h i s t o p i c t o the  l a t e r c h a p t e r on'the comparative  study o f c o n t i n u o u s  p u l s a t i o n s a t s t a t i o n s of d i f f e r e n t l a t i t u d e s and d i f f e r e n t longitudes. The example g i v e n i n P i g . I I I . 3 c i s a t y p i c a l o b s e r v a t i o n a t R a l s t o n under q u i e t magnetic c o n d i t i o n s ( £K Pc3  = 3 i n this case.).  As shown i n the spectrogram,  shows an i n v e r t e d U-type d i u r n a l v a r i a t i o n w i t h a maximum  f r e q u e n c y o c c u r r i n g around noon.  The d i f f u s e d s t r u c t u r e i s  t y p i c a l f o r a q u i e t day under s t e a d y c o n d i t i o n s . t h e b o u n d a r y b e t w e e n t h e m o r n i n g and a f t e r n o o n may  type o f Fc3  S o o n a f t e r 1600 L.T. t h e s e c o n d  be i d e n t i f i e d .  of h i g h e r  frequency takes  over.  T h e r e i s some  Pc'l i s o b s e r v e d o n l y q u i e t and s t e a d y m a g n e t i c  r a r e l y a t R a l s t o n under  very  conditions.  p a r t i c u l a r c a s e where we do n o t o b s e r v e Pc3  i n t h e m o r n i n g may o c c a s i o n a l l y t a k e  place  at Ralston.  i n P i g . I I I . 3 d c o n t a i n s most i m p o r t a n t  example g i v e n  b y H i r a s a w a and N a g a t a .  type i s very  shown  sonagram i n t h e l o w e r p o r t i o n o f P i g . I I I . 3 c  i n the contoured  reported  train  overlapping  o f f r e q u e n c y b e t w e e n t h e two t r a i n s a s i s c l e a r l y  The  A t 1530 L .  rare at Ralston.  An  features  The o c c u r r e n c e o f t h i s  I t occurs  o n l y when t h e  magnetosphere i s .expanding r a p i d l y (see t h e Appendix 1 f o r the  table of K  D  index).  There i s another f e a t u r e which i s very i n t e r e s t i n g and  common t o most s p e c t r o g r a m s o b s e r v e d a t R a l s t o n .  b e e n n o t i c e d t h a t e v e n f o r t h e most c o n t i n u o u s observed, a 'blank take place  place.  This  abruptly,  1  occurred  often  activity  takes  and i t d o e s n o t a f f e c t t h e c o n t i n u i t y o f t h e  p u l s a t i o n event i n other disturbed  events  o f 20 t o 60 m i n u t e i n t e r v a l may 'pause' o f m i c r o p u l s a t l o n  I t has  time i n t e r v a l s .  conditions this  a b r u p t pause o f a c t i v i t y  e a r l y i n the afternoon,  the pause i s found e a r l i e r  Under m i l d l y  but there  i n the morning.  usually  a r e c a s e s where  45  In Pig.III.3b, for  t h e pause  a b o u t h a l f an h o u r .  occurred  a t 1345  L.T.  The  was  pause  a t 1230  L.T.  and  lasted  o f t h e F e b r u a r y 10  and l a s t e d o n l y  event  about t e n minutes  (see  Pig.III.3c). The  March  under d i s t u r b e d  19 e v e n t shown i n F i g . I I I . 3 e t o o k conditions  (^K  = 29).  The  pause  place of  this  P p a r t i c u l a r event occurred  i n the morning.  i n a l l t h e c a s e s shown, t h e p a u s e frequency range.  The  and F i g . I I I . 3 © a r e n o t  took place  Pc4 i n b o t h e x a m p l e s affected.  I t i s noted only  that  i n the  Pc3  shown i n F i g . I I I . 3 b  TVPt B, BS SON A a RAM •  KAY ELECTRIC CO.  PINE BROOK. N. J.  - «  U.T. — •  L.T.  6  8  10 12 14 16 18 20 22 00 2  4  6  • i i i • I • I • I • I • I • I • I ' I • I • I • I  23 1  3  5  7  9  T I M B aa (ONAOffAM •  11  13 15 17  KAY KLECIRJC CO.  PINK BROOK. M. X  FIG lll.3a RALSTON X 18 OCT67 NORMAL TYPE WITH MORNING AND AFTERNOON SEPARATION  19 21 23  47  FIG III.3b RALSTON X NORMAL TYPE UNDER DISTURBED  7 DEC 67 CONDITIONS  48  FIG 111.3c RALSTON X  FEB10,67  NORMAL TYPE UNDER QUIET  CONDITIONS  49  FIG lll.3d  RALSTON X  30 OCT 67  AFTERNOON TYPE OF Pc3  5 0  FIG lll.3e RALSTON X THE  MAR 19,67  'PAUSE' THAT OBSERVED I N THE MORNING  51  111.4  THE  I N V E R T E D U - T Y P E V/ITH D I S C R E T E  Very quiet  variation  has  been  spectrum  is  at  often take  time  about h a l f  r e g u l a r time  of the  order  of  maximum f r e q u e n c y rule  at Ralston, under  i n frequency.  may  The  usually  occur  observed  has  between  hour  around  the  dynamic  discrete  width  local  governing  the  they  minutes.  of  anything  successive  although The  ten to twenty  been observed  U-type  other workers,  intervals.  appears  inverted  a spike-like  interval t o one  an  moderately  Further, unlike  so f a r r e p o r t e d b y  o f Pc3  appearance. is  Pc3  c o n d i t i o n s (Kp<;2) b e h a v e s a s  diurnal that  often,  STRUCTURE  spikes  do  not  of each The  spike  spike  noon, but  occurrence  no of  of definite  such  spikes. Two Both  examples are  events  magnetic  shown o c c u r u n d e r  conditions indicated  values of the The the  Kp  U-type  types mentioned a discrete  type. unique.  We  are Only  the  low  structured  Pc3  i s not  i n the  too  but  type well  behaviour.  previous three We  steady  fluctuating  in this  aware t h a t t h i s  when t h e  restricted A l l the  s e c t i o n s may  to  other also  p r e f e r t o c o n s i d e r them as  mentioned  physical  becomes b e t t e r u n d e r s t o o d manner.  not  by  of d i u r n a l  appearance.  of the  q u i e t but  F i g . III.4b.  and  index.  spike-like  inverted  mixture  g i v e n i n F i g . III.4a  can  and  classification  nature  one  section  of  classify  these  take  a  their  own  i s not  spikes  them i n a  strict  FIGIIWa RALSTON X 26 MAR 67 INVERTED U-TYPE WITH DISCRETE STRUCTURE  53  FIG lll.4b RALSTON X  28 DEC 67  INVERTED U-TYPE WITH DISCRETE STRUCTURE  54  III.5  THE DIFFUSED INVERTED U-TYPE T h e r e i s a n o t h e r t y p e o f Pc3 a c t i v i t y  R a l s t o n which  observed at  a l s o d i s p l a y s an i n v e r t e d U-form o f d a i l y  v a r i a t i o n i n frequency.  A sonagram o f t h i s t y p e  shows a  c o n t i n u o u s t r e n d w i t h no p a r t i c u l a r p r e f e r e n c e f o r a maximum i n t e n s i t y a t a n y p a r t i c u l a r t i m e therefore called  t h i s type of a c t i v i t y  a  interval. 'diffused'  i n v e r t e d U-type i n c o n t r a s t t o t h e ' d i s c r e t e ' U-type d e s c r i b e d i n t h e l a s t The and  inverted  section.  d i f f u s e d i n v e r t e d U-type o c c u r s o n l y under  reasonably q u i e t magnetic  s h o u l d be e m p h a s i z e d , the  conditions.  The word  t h e mean v a l u e t h a t we may o b s e r v e whereas t h e d i s c r e t e  the d i f f u s e d  'steady'  reasonably f l u c t u a t i n g .  from  inverted  i n v e r t e d U-type o f d i u r n a l  v a r i a t i o n t a k e s p l a c e o n l y when t h e m a g n e t i c  this diffused  steady  b e c a u s e i t i s o n l y when t h e v a l u e o f  index does n o t f l u c t u a t e over a c e r t a i n l e v e l  U-type,  We  condition i s  Of c o u r s e , one may a l s o t h i n k o f  type as o n l y a p a r t i c u l a r case o f t h e d i s c r e t e  type w i t h t h e s p i k e s crowded t o g e t h e r . In Table  III.2,  i n v e r t e d U-type Pc3.  we have l i s t e d  8 c l e a r days o f d i f f u s e d  A l l the events l i s t e d  i n Table  III.2  h a v e Z K p l e s s t h a n 15 b e c a u s e we h a v e n o t b e e n a b l e t o f i n d any  good e x a m p l e o f t h i s t y p e where t h e v a l u e o f £Kp i s g r e a t e r . The  average  frequency of events l i s t e d  i s 3 0 mHz, w i t h  v e r y s m a l l v a r i a n c e , and t h e most p r o b a b l e t i m e f o r maximum  55  f r e q u e n c y t o t a k e p l a c e i s around  1300  L.T.  Most  u n d e r s t u d y h a v e maximum f r e q u e n c y o c c u r r i n g one b e f o r e o r a f t e r 1300  cases hour  L.T. TABLE  III.2  DATES OP DIFFUSED INVERTED U-TYPE DIURNAL V A R I A T I O N OF Date  F  FREQUENCY mHz  L.T.  max  Nov  17, 1967  3_  30  1200  Nov  18, 1967  5_  .29  1200  Oct  20, 1967  6_  29  1330  Nov  19, 1967  6  30  1430  f  +  Mar  17, 1967  30  1230  Oct  16, 1967  30  1230  Aug  22, 1967  l l _  25  1330  Mar  28, 1967  ^ 6  35  1400  Two  e x a m p l e s o f t h e D.I.U. t y p e o f d i u r n a l  a r e shown i n P i g . I I I . 5 a and F i g . I I I . 5 b where t h e U-shape i s most c l e a r . s t r u c t u r e Pc3  listed  may  However, some of. t h e  variation inverted  diffused  b e h a v e somewhat d i f f e r e n t l y .  the main peak i n f r e q u e n c y o b v i o u s i n a l l c a s e s t h e r e e v e n t s t h a t have s e c o n d a r y b e f o r e dusk. where two  One  peaks o c c u r r i n g near  such example i s i l l u s t r a t e d  secondary  p e a k s a r e shown, one  Besides are  dawn o r  i n F i g . III.5c  a t 0600 L.T.  and  the  5 6  other at 1 6 0 0  L.T.  The o c c u r r e n c e o f a s e c o n d a r y  a r o u n d dawn o r d u s k i s n o t uncommon a t R a l s t o n .  peak  57  FIG 111.5a RALSTON X 16 OCT 67 INVERTED U-TYPE WITH DIFFUSED STRUCTURE  58  FIG 111.5b RALSTON X  19 NOV 67  DIFFUSED TYPE OF DIURNAL STRUCTURE  59  FIG 111.5c RALSTON X  17 NOV 67  DIFFUSED INVERTED U-TYPE WITH SECONDARY MAXIMA  60  III.6  MIXED CASES OF I t has  THE  FOUR BASIC TYPES  been o b s e r v e d t h a t the g r e a t m a j o r i t y of  e v e n t s o c c u r r i n g a t R a l s t o n may of, or the  combination  be  subclassified  of, the f o u r b a s i c types  v a r i a t i o n of frequency  described  sections.  been prepared  A t a b l e has  o v e r a p e r i o d o f t h r e e m o n t h s i n 1967 according  to t h i s  scheme ( s e e T a b l e  In order a s k e t c h has of Table  been p r e p a r e d  III.3.  i d e a a s t o how But  one  t o show t h e  steady  the  taken  The  before  III.3).  i n the  provide  type.  t h a t the  one  On  the  e x a m p l e , x^  appearance of the  observation  i s best  third  l i m i t a t i o n o f Kp  column rough  index,  and  draws f u r t h e r c o n c l u s i o n s .  d e s i g n a t i o n s x^,  For  disturbance,  us w i t h a  x^,  and  x^  s i g n i f y the  of each i n d i v i d u a l event w i t h r e s p e c t t o each basic  subclassified  p l a n e t a r y magnetic disturbance i s .  must b e a r i n m i n d t h e  c a r e must be  have been  f o r e a c h day may  four  spectrograms  l e v e l of magnetic  These s k e t c h e s  one  of d i u r n a l  i n the p r e v i o u s where  into  quality  particular  shown u n d e r Type 1 w o u l d mean  spectrogram f o r t h i s  particular  a p p r o x i m a t e d t o Type 1 d i u r n a l v a r i a t i o n .  o t h e r h a n d , x ^ and  x^  shown u n d e r Type 2 and  Type  respectively,  i n d i c a t e t h a t t h i s e v e n t a p p e a r s t o behave  a combination  o f Type 2 and  Type 2  Pc3  Type 4 d i u r n a l v a r i a t i o n  4 as  with  dominating. Examples are g i v e n i n F i g . I I I . 6 a - e  the e x i s t e n c e of  some o f t h e  possible  to  demonstrate  combinations.  61  In F i g . I I I . 6 a , v a r i a t i o n may inverted  be  t a k e n as  U - t y p e and  the  boundary between the place  an e x a m p l e i s shown whose d i u r n a l '  m o r n i n g and  m o r n i n g and  a r o u n d n o o n and  the  t h r o u g h o u t most o f t h e In Fig.III.6b structure  e a r l y i n the  afternoon,  where t h e  afternoon types  i n v e r t e d U-type has  morning, but  takes  i s apparent  the  appearance of L.T.  the  and  in  A s i m i l a r e x a m p l e i s shown i n F i g . I I I . 6 c appears i n the  morning  rather  afternoon. d i f f u s e d i n v e r t e d U-type w i t h  normal type i s demonstrated i n yet In F i g . I I I . 6 e  the  c o m p l i c a t e d t h a t each of the b e h a v i o u r may  The  discrete  d i f f u s e d t y p e a f t e r 1100  C o m b i n a t i o n of the  Fig.III.6d.  afternoon type.  spike-like structure  diffused structure  t h a n i n the  discrete  day.  the  spectrogram i s of the the  a c o m b i n a t i o n of the  be  identified.  a n o t h e r e x a m p l e shown i n  spectral pattern  four  the  basic  types of  shown i s diurnal  so  62  TABLE SUB-CLASSIFICATION  Date  Type  1967 Oct  ^  1  Oct  2  Oct  3  Oct  4  Oct  5  Oct  6  11  SOME  1  Type  Fc3  2  EVENTS  Type  Type  4 Mi sc  Variation  3  JL  +  5_ 8  X X,  0  x.  24  O c t 13  171 0  O c t 14  21_  +  w X  2  x  4  x.  x. X,  18  O c t 18  14_  O c t 19  9  X,  ^3  0  x  n  0  Oct  20  Oct  23  Oct  24  Oct  25  \  Oct  26  5_  Oct  27  l 8  Oct  28  30_  Oct  29  29_  Oct  30  19  X,  X,  16  O c t 17  3  X,  o  1 2  3  l  O c t 12  Oct  OF  + 9  1  III.3  6_  v  l  x.  o  -A X,  X  3  63  Date  v  Kp  K  1967  Nov  3  2  Nov  4  16  Nov  5  Nov  6  Nov  8  Nov  9  Type  Variation  p  I  1  Type j .'-^  2  3  Type •  1  Type  4 Misc.  1  ^o  \.  18  8  , yv-...  Nov  10  Nov  13  Nov  14  Nov  15  Nov  16  17' 0  Nov  17  3.  Nov  18  5  Nov  19  6  0  19_  x  2  x  3  2  X  2  x  X., X  2  X  2  3  v  3  Nov  23  16_  Nov  24  27_  Nov  25  Nov  28  Nov  29  Nov  30  o  +  3  x.  x  X  2  X  2  X  3  X  3  X  2  -  —  +  20  3  X  l  X  l  X  l  .  * x  X  2  X  3  X  2  X  3  x  3  - • _^...-  3 X.  v  x  X-  3  x  21  X  0  Nov  24  2  X  +  3  x„  x  3  x  3  X,  64  D  a  t  _  e  K  / K „p  1967  Type  p  u V a„ r„ i, -a „t ni „o „n  |1.-^  Dec  4  14.  Dec  5  1  Dec  6  28  Dec  7  27  Dec  8  31  X,  Dec  9  18  X,  Dec  10  12  Dec  11  5  Dec  12  Dec  13  10_  Dec  19  31  Dec  20  33.  Dec  21  24  Dec  22  Dec  24  11_  Dec  25  6  Dec  27  v  o  1  2  L  2  1  29  9 10  Dec  30  18  Type l.-x  2  X.  3  Type  4  I .1; ::  MiSC  X,  v  3  ^3  X X,  3  X. X,  o  x. X.,  X  X,  X,  X,  3  X.,  "V  .  Dec  X,  o  c  28  2  X,  c  Dec  I .-X  2  +  c 1 6  Type  l  X  +  1  X  X.  A  + \  X,  ^3  k  2  C  3  65  FIG III. 6a RALSTON X  7 SEPT 67  COMBINATION OF THE DISCRETE INVERTED U-TYPE AND THE MORNING AND AFTERNOON TYPE  66  FIGIII.6b RALSTON X MIXED  4 OCT 67  INVERTED U-TYPE OF DISCRETE AND DIFFUSED STRUCTURE  67  FIG 111.6c RALSTON X MIXED  26 OCT 67  INVERTED U-TYPE OF DISCRETE AND DIFFUSED STRUCTURE  6 8  FIG lll.6d  RALSTON X OCT 25.67  MIXED INVERTED U-TYPE .AND NORMAL TYPE  69  FIG lll.6e RALSTON X  1 SEPT 67  MIXTURE OF A L L U BASIC TYPES  70  III.7  MISCELLANEOUS TYPES The  diurnal variation  complicated  o f Pc3 a t R a l s t o n  when t h e p l a n e t a r y m a g n e t i c  u n s t e a d y o r when t h e c o n d i t i o n i s v e r y However,  the research  concerned  only  disturbed  conditions.  the  continuous  with  any of  values  of  fluctuating.  other  index  level  study i s high.  are four examples given n o t be c l a s s i f i e d  i n the previous examples.  to mildly  h a s b e e n made t o  b, c, and d t h a t c o u l d  many  thesis i s  quiet  p u l s a t i o n when t h e d i s t u r b a n c e  of that described course,  In this  Pc3 t h a t b e h a v e s u n d e r  In the f o l l o w i n g , there Pig.III.7aj  conditions are disturbed.  undertaken  No a t t e m p t  b e c o m e s very-  section.  or they  into  There a r e ,  we h a v e n o t i c e d  are e i t h e r too high  In  that  their  are very  7 1  FIGW.7a  RALSTON X FEB 23,67  MISCELLANEOUS TYPES  72  FIG lll.7b  RALSTON X 12 OCT 67  MISCELLANEOUS  TYPES  7.3  FIG 111.7c  RALSTON X  MAR 18.67  MISCELLANEOUS TYPES  7 4  FIGIII.7d  RALSTON X  29 OCT 67  MISCELLANEOUS TYPES  7 5  III.8  INTERPRETATION OF Many r e s e a r c h e r s  RESULTS AND  DISCUSSION  b e l i e v e t h a t t h e Pc4  t i o n i s c a u s e d by a h y d r o m a g n e t i c wave, and  range of p u l s a that  h y d r o m a g n e t i c wave p r o p a g a t e s a l o n g  the  plasmapause d i s c o v e r e d  (1966), whereas  Pc3  the  Experimental (1966) and  the  the  evidence  N a g a t a and  and  Pc4  provided  Fukunishi  frequency,  between e x p e r i m e n t a l  By  by H i r a s a w a and  Nagata  (1968) g i v e s f u r t h e r  support  studying  these  The  theoretical  c o n f i g u r a t i o n r e p o r t e d by C a r p e n t e r Carpenter  has  found  of the  disturbed indeed  (K  p  4).  I f the Pc3  a s t a n d i n g wave s e t up  the ionosphere,  by H i r a s a w a and e x i s t e n c e o f one  and  i t should  the  i s moderately  range of p u l s a t i o n i s  and  minimum p e r i o d  T h i s i s e x a c t l y the case found  of the  and  b e h a v e as a d i u r n a l v a r i a t i o n  Nagata (1966). two  Pc3  the  shortest  between the plasmapause  maximum p e r i o d a r o u n d 2000 L.T.  a b o u t 0600 L.T.  plasmapause  shown, t h e g e o c e n t r i c d i s t a n c e o f  when t h e g e o m a g n e t i c f i e l d  = 2 —»  calculation  (1966) u s i n g w h i s t l e r  p l a s m a p a u s e i s l a r g e s t a t a b o u t 2000 L.T. a b o u t 0600 L.T.  agreement  at Japanese s t a t i o n s  i s b a s e d on g e n e r a l d i u r n a l b e h a v i o u r  As  the d i u r n a l ' v a r i a t i o n  authors  r e s u l t s obtained  with theoretical prediction.  data.  between  ionosphere.  the above p o s t u l a t i o n s .  of P c 3  has  at  A l f v e n mode ( p o l o i d a l o s c i l l a t i o n ) e x i s t i n g  t h e p l a s m a p a u s e and  at  line  r a n g e o f p u l s a t i o n i s t h o u g h t o f as a s t a n d i n g wave o f  modified  to  by C a r p e n t e r  field  this  I t may  that at  experimentally  also explain  bands o b s e r v e d a t  the  Ralston  76  (Pig.Ill.2b).  The  that  observed  band  shown i n T a b l e  why  there  are  observed  of  the  Pc  and  and  they  band t h a t  and  III.l.  Pc3  Nagata  with  mHz)  occurrence  to  the  Pc4  the  two  Pc3  bands.  and  mHz  is  always  (1953),  found  58.4°) s h o w  peaks  at  60  sec  (Pc4)  this  to  the  different  which  38  to  explain  band  Holmberg ( d> =  closest  i s the  why  at Eskdalemuir  a fundamental frequency  (35  period  and  (1966),  attribute  has  I t r e m a i n s f o r us  bands,  Usher  spectra  micropulsation  period, of  two  Hirasawa  simultaneously  Stuart that  by  frequency  and  25  sec  (Pc3)  harmonics  shows p r e f e r e n c e  at  Eskdalemuir. One structure could  of  theory  o f f e r e d by  observational  be  result for  Stuart  standing  f a r , we  another  this  although  as  of  of  multi-band at  Ralston  different  demonstrated to the  that  e x p l a i n some existence  different  a theory  3)•  field  plasmapause  wave,  be  Usher f a i l s  of  harmonics  we  have  the  of  ( D e r i v a t i o n of  Therefore,  have p o s t u l a t e d the  the  can this  to  look  theory.  p o s t u l a t i o n to  standing  presence  i t may  a result  altogether  wave a l o n g  between the  the  f a c t s found,  a more f a v o u r a b l e  extend  and  i s shown i n a p p e n d i x  So  also  by  However,  s t r u c t u r e as  disproved  t o wonder whether  p u l s a t i o n events observed  explained  involved.  multi-band not  then begin  continuous  i n t u r n be  harmonics  the  would  only  line and  the  include  s e t up  at  the  existence  of  plasmapause  ionosphere.  the  i n the  the  If  a and  we  possible existence  plasma-trough  outside  of  •  7 7  t h e p l a s m a p a u s e , t h e n t h e f o l l o w i n g must be The  considered.  p o s i t i o n of R a l s t o n i s s i t u a t e d very c l o s e to  f o o t of the f i e l d  l i n e d e f i n i n g the average e q u a t o r i a l  p o s i t i o n of the plasmapause.  Suppose t h e r e i s a t i m e  R a l s t o n i s at the plasmapause which i s very probable moderately  d i s t u r b e d c o n d i t i o n s , and  i n t e r v a l of time,  at that  of these  f^ respectively.  frequency  range.  particular  As  i n the plasmatrough.  Both  a result,  f ^ and  f ^ are i n  Let  regions Pc3  s u p e r p o s i t i o n of these  waves w o u l d p r o d u c e an o s c i l l a t i o n o f t h e m a g n e t i c  two  under  s t a n d i n g waves f o r t h e two  be f ^ and  observed  when  t h e r e i s s t a n d i n g wave o f p o l o i d a l mode  e x i s t i n g i n t h e p l a s m a s p h e r e , and eigen-frequency  two  field  a t R a l s t o n t h a t upon s p e c t r a l a n a l y s i s s h o u l d  distinct  f r e q u e n c i e s f ^ and  f^.  Furthermore,  yield  i f the  c o n f i g u r a t i o n o f t h e p l a s m a p a u s e on t h a t p a r t i c u l a r d a y such t h a t R a l s t o n remains i n the v i c i n i t y of the boundary f o r a c e r t a i n l o n g i n t e r v a l of time,  and  p o s s i b l e because the plasmapause i s a c o n t i n u o u s d i m e n s i o n a l b o u n d a r y , one  would expect  p a r t i c u l a r time  interval  f^  v a r i a t i o n o f f ^ and  and  f^.  The  d i f f e r e n t dimension To to  mid-latitude  to f i n d  knee this i s three  i n that  f ^ would m a n i f e s t  o f t h e p l a s m a s p h e r e and  of multi-band  stations,  is  a two-band s t r u c t u r e w i t h f r e q u e n c i e s  see w h e t h e r t h i s I s i n d e e d  the occurrence  the  one  has  the  the  plasmatrough.  situation that  s t r u c t u r e d Pc3 to take  the  observed  simultaneous  t i o n s a t t h e h i g h as w e l l a s a t t h e l o w l a t i t u d e  leads in  observa-  stations.  7o  We s h a l l a later  report the result  h a s been w i d e l y r e c o g n i s e d t h a t  phenomenon t h a t  i scaused  s e t up a l o n g t h e f i e l d be a c c e p t e d ,  (f^) in  band  by a standing hydromagnetic  line  o f t h e above  postulation structure  Fig.III.-8  i s an attempt  expansion  and c o n t r a c t i o n  the plasmatrough  (poloidal  a t t h e plasmapause.  then the simultaneous  p l a s m a p a u s e when m u l t i - b a n d  periodic  oscillations).  EIGEM The morning  using.the  that  occurrence  of both  t h e plasmasphere respectively i salso  this  type  shown.  III.8 IN  taking  asymmetry o f t h e p l a s m a s p h e r i c On t h e d a y t h a t  be e x p l a i n e d  to represent graphically the  THE  o f t h e normal  after  o f t h e Pc4  takes place.  MAGNETOSPHERE type  diurnal  a n d a f t e r n o o n s e p a r a t i o n may a l s o  same m o d e l  wave  Ralston i sa t the  Pc4 ( f , f r e q u e n c y )  OSCILLATIONS  localised  I fthis i s  occurrence  o f f ^ and f ^ f r e q u e n c y  FIG.  with  Pc4 i s a  w i t h t h e o t h e r t w o P c 3 b a n d s may a l s o  the light  and  observationsi n  chapter. It  to  o f some o f t h e s e  into  account  configuration  o f Pc3 d i u r n a l  variation  be e x p l a i n e d t h e dawn-dusk  ( C a r p e n t e r 1966) 0  variation  takes place,  79  Ralston  i so u t s i d e t h e plasmasphere  boundary between t h e morning therefore Ralston  be t a k e n  i sgoing  sphere.  of  outside to the inside  apparent  Ralston the  and t h e a f t e r n o o n type  crossing  o f t h e plasma-  may b e  to explain  begins  the boundary  understood  the occurrence  at Ralston.  would  The f r e q u e n c y  Therefore,  Pc3 would  with  experimental results  decrease  inverted  maximum f r e q u e n c y explained has  of the afternoon  with time.  reported e a r l i e r  U-pattern  This  Pc3 w i t h  0600 L . T . c o u l d b e also  (1969), u s i n g d a t a o b t a i n e d  a s y m m e t r y may e x i s t  on P i o n e e r i nthe solar  asymmetry i s i n t r o d u c e d by t h e i n f l u e n c e  streams.  type  chapter.  asymmetry.  t h e M.I.T. p l a s m a e x p e r i m e n t  rotation  agrees  i nthis  o f the morning  o c c u r r i n g around  as  of the inside of  the frequency  rapidly  Recently,. Siscoe e t a l  east-west  the  o f Pc3 o b s e r v e d a t  t o o i f t h e r e g i o n o u t s i d e t h e plasmapause  an east-west  from  t h e plasmasphere,  now d e p e n d o n t h e d i m e n s i o n  plasmasphere.  The  into  t o g i v e way t o t h e new a f t e r n o o n t y p e  type  The  when  m u l t i - b a n d Pc3.  morning type  an  o f Pc3 w o u l d  of boundary c r o s s i n g  t h e same r e a s o n i n g we o f f e r  After  is  The  The o v e r l a p p i n g o f f r e q u e n c i e s a t t h e b o u n d a r y  between the morning with  and a f t e r n o o n type  as evidence  from  i n t h e morning.  on t h e i n t e r a c t i o n The f a s t  stream  between f a s t  would  tend  6,  found  wind  that  velocity.  o f t h e sun's  and slow  t o come f r o m  plasma t h e west  and t h e s l o w one f r o m t h e e a s t s o l a r wind d i r e c t i o n .  The  v/ith r e s p e c t  existence  t o the  o f an e a s t w a r d  component o f s o l a r w i n d v e l o c i t y w o u l d p r o d u c e west a s y m m e t r y o f t h e m a g n e t o s p h e r e . is  subjected  average  As t h e  an  east-  magnetosphere  t o c o m p r e s s i o n by s o l a r w i n d w i t h an e a s t w a r d  v e l o c i t y c o m p o n e n t , t h e d i m e n s i o n on t h e dawn s i d e o f t h e magnetosphere  outside  t h e p l a s m a s p h e r e w o u l d be  t h a n t h a t on t h e a f t e r n o o n plasmapause  side.  The  smaller  region outside  i s more s e n s i t i v e t o c o m p r e s s i o n b e c a u s e  i t s l o w p a r t i c l e d e n s i t y , and t h i s r e s u l t g i v e s experimental the  support to the theory  we  of  further  offered to e x p l a i n  d i u r n a l b e h a v i o u r of the normal type w i t h morning  afternoon  and  separation.  The  i n v e r t e d U-type  of d a i l y v a r i a t i o n of frequency  o f P c 3 w i t h b o t h d i f f u s e d and d i s c r e t e s t r u c t u r e o n l y under m a g n e t i c a l l y  plasmapause  occurred  C a r p e n t e r (1967)  quiet conditions.  observed that during very the  the  q u i e t p l a n e t a r y magnetic  a p p e a r s t o assume a more n e a r l y  configuration at I t s l a r g e r radius.  According  condition  circular to  this  r e p o r t t h e d i m e n s i o n o f t h e p l a s m a s p h e r e becomes so l a r g e u n d e r t h e s e q u i e t c o n d i t i o n s t h a t R a l s t o n w o u l d be i n s i d e the plasmasphere t h r o u g h o u t the day. no b o u n d a r y  c r o s s i n g should  i n v e r t e d U-type the  theory  be o b s e r v e d ,  found  That I s t o say,  To e x p l a i n t h e  d i u r n a l b e h a v i o u r , one h a s t o go b a c k t o  of the formation  of the  plasmapause.  81  The interpreted  f o r m a t i o n of plasmapause (Nishida,  1966)  theoretically  as due t o a s u p e r p o s i t i o n o f t h e  two d i f f e r e n t k i n d s o f d y n a m i c .plasma, n a m e l y  has been  motion of the magnetospheric  t h e c o - r o t a t i o n w i t h t h e E a r t h and t h e  c o n v e c t i v e m o t i o n i n the magnetosphere  d r i v e n by  solar  wind.  The m e c h a n i s m t h a t p r o v i d e s a d r i v i n g f o r c e t o m a i n t a i n t h e c o n v e c t i v e m o t i o n i n the magnetosphere terms o f Dungey's model (1961). Nagata  i s best described i n  I t h a s b e e n shown b y  (1967) t h a t .the p o l a r S P - f i e l d w h i c h i s c o n s i d e r e d  a s c a u s e d by t h e m a g n e t o s p h e r i c c o n v e c t i o n becomes p r a c t i c a l l y n u l l when t h e Kp i n d e x a p p r o a c h e s z e r o .  This  result  s u g g e s t s t h a t d u r i n g t h e q u i e t e s t c o n d i t i o n t h e r e may i n t e r a c t i o n between  be  no  t h e s o l a r w i n d and t h e m a g n e t o s p h e r i c  p l a s m a , whence t h e s o l a r w i n d p r e s s u r e c a u s e s s i m p l y a c o m p r e s s i o n of the magnetosphere  i n c l u d i n g the  plasmapause  on t h e n o o n s i d e , t h u s m a k i n g t h e e i g e n f r e q u e n c y o f t h e s t a n d i n g h y d r o m a g n e t i c wave o f m o d i f i e d A l f v e n mode i n s i d e the plasmasphere U-type  of d a i l y The  largest  around noon,  that i s ,  an  inverted  variation.  dawn s i d e s h i f t  of the boundary between  o f t h e maximum f r e q u e n c y and  m o r n i n g and a f t e r n o o n t y p e o f  c o u l d a l s o be e x p l a i n e d b y N i s h i d a ' s t h e o r y o f t h e  also  Pc3  plasma-  p a u s e when t h e v a l u e , o f t h e Kp i n d e x becomes l a r g e r ,  AS  N i s h i d a h a s a l r e a d y shown, t h e l o c a l t i m e c o r r e s p o n d i n g t o t h e minimum g e o c e n t r i c d i s t a n c e o f t h e p l a s m a s p h e r e  shifts  t o w a r d s t h e dawn s i d e a s t h e c o n v e c t i v e m o t i o n i s i n t e n s i f i e d .  8 2  This again agrees w i t h experimental previous  sections.  r e s u l t s mentioned  i n the  33  CHAPTER  _Kp„ - D E P E N D E N C E  IV.1  spheric  comparison of  boundary,  satellite, Amazeen  with  radius  of  the  M I, D - L A T I T U D E  index  been motivated the  frequency  observed  an  by  inverse  relation I f the  Pc3  i t s resonators, of  range  resonators,  one  Pc3  Troitskaya,  would  1964;  and  of Alfven  since  depends expect  p u l s a t i o n on  12  and  b e t w e e n Kp  poloidal oscillation  frequency  Explorer  waves of m o d i f i e d  magnetospheric  and  the  magneto-  indices, Cahill  standing  the  by  the  on  to  find  the  Bolshakova,  the  Kp 1965a;  a l , 1966). The  which  the  (Bolshakova  Nagata et  p o s i t i o n of  magnetosphere.  of  dimension of of  the  directly  i n the  frequency  dependence  to  I.N  corresponding  i s caused  mode e x i s t i n g eigen  as  (1963) o b s e r v e d  pulsation  the  Pc3  INTRODUCTION By  the  OF  IV  research by  a desire  different  types  subclassified  occur.  t o be  Further,  to f i n d of  i f the  existence  observed  Ralston  i s to  obtained  magnetic  could  activity  be  chapter  precise  last  chapter  p h y s i c a l nature  f o r the  k n o w l e d g e m u s t be  the  in this  of  each of  of  may of  the  the Pc3  affect  how  different  each of  the  under  Pc3  be  better understood,  of  has  condition  diurnal variation  i n the  responsible at  reported  expected mechanism  bands a  levels  precise of  individual  bands.  84  C o r r e l a t i o n between t h e f r e q u e n c y and  t h e Kp i n d e x h a s b e e n f o u n d  researchers Fukunishi, observed and  e x p e r i m e n t a l l y b y many  ( M c N i c o l and M a i n s t o n e , 1968; B o l s h a k o v a ,  of Pc3 p u l s a t i o n  1963; N a g a t a a n d  1965).  Bolshakova  (1965)  an i n v e r s e dependence o f t h e Pc p e r i o d s  (Pc2, Pc3  P c 4 ) o n Kp w h i c h i s g i v e n b y a n e m p i r i c a l e x p r e s s i o n . T  p c  = 58.3 - 8.25  K  N a g a t a and F u k u n i s h i (1968) a l s o f o u n d linear  p  an  r e l a t i o n between t h e e i g e n f r e q u e n c y  approximately o f magnetic  p u l s a t i o n a n d t h e a v e r a g e v a l u e o f Kp ( K p ) a s w e l l a s ][Kp and they d e r i v e d e m p i r i c a l l y a n u m e r i c a l f o r t h e maximum c e n t r a l f r e q u e n c y  expression  ( f ) o f P c 3 and Pc4 m  p u l s a t i o n s w h i c h i s g i v e n by f  m  (mHz) = 11 + 4.5 K  f o r t h e - 1 5 mHz P c 4 b a n d  f  m  (mHz) = 2 0 + 7  f o r t h e 35 mHz P c 3 band  Both equations  will  Kp  be p l o t t e d  i n F i g . IV.2a i n t h e next  section. A s i m i l a r l i n e a r r e l a t i o n s h i p b e t w e e n t h e maximum central  frequency  o f each o f t h e P c 3 bands o b s e r v e d  R a l s t o n a n d Kp h a s b e e n o b t a i n e d . bands d e s c r i b e d i n t h e l a s t differently  disturbances. light  Each o f the three Pc3  c h a p t e r has been found  subject to different  at  t o behave  l e v e l s o f magnetic  Such d i f f e r e n c e s have been s t u d i e d i n t h e  o f r e s u l t s r e p o r t e d e a r l i e r by o t h e r  authors.  85  Different have been found The  result  types  of d i u r n a l  to occur  of t h i s  variation  under d i f f e r e n t  observation w i l l  be  o f Pc3  magnetic  presented  frequency conditions.  i n the  next  section. Experimental  evidence  shown t h a t s u d d e n e n h a n c e m e n t  gathered o f Pc3  an a b r u p t  increase i n the value  pretation  of o b s e r v a t i o n a l f a c t s  section.  i n section activity  o f t h e Kp  IV.3  may  index.  Is offered  i n the  has  occur An  with  inter-  last  86  IV.2  K  - DEPENDENCE  p  In each  order  of the three  different values  o f K^,  FREQUENCY  t o i n v e s t i g a t e how t h e m e a n f r e q u e n c y  of  P c 3 b a n d s f „ , f ~ a n d f.. w o u l d  to  magnetospheric extreme  identification Such  OF THE Pc3  Identification  conditions represented  care  of each  must be t a k e n  of these  i s made  only  after  i n Pc3 s p e c t r a l  signals  are properly interpreted with  Chapter  with  K  P  I I I .  Thus,  i s meaningful  investigated  may d e f i n i t e  behaviour  be In  that  have  data.  the variation  and o n l y w i t h  not  exceed  such  this  chapter,  we  criterion  one, t h a t  shall  constant  o f t h e Kp i n d e x  o f Pc3  a n d Pc-3 o f t h e model  frequencies  a constant  K  P  are  preliminary  evidence  I s such  of  systematic  cases  must n o t o c c u r  = 0 to L  = 2.  compiled  listed  i n Table  the  values  of ZK  that fluctuation of  K  twice  each  should  = 1, t h e  of t h e extreme  a day.  v/ith t h e above mentioned  IV.1, where  day  d a y m u s t be w i t h i n t h e  Further,  more t h a n  days  o f K^ f o r o u r b a s i c  i s , f o r a day l a b e l l e d  of L  are  only those  w i t h i n an i n d i v i d u a l  range  Data  select  value  o f Kp w i t h i n t h a t p a r t i c u l a r  with  of diurnal  the help  a careful  value  along  reliable  obtained.  The w o r k i n g  value  the type  i f days w i t h  and r e l i a b l e  approximately  the  different  t o ensure  s t r u c t u r e I s determined  only  selection  by  bands under c o n s i d e r a t i o n .  pattern  in  respond  the values  criterion  o f Kp a s w e l l  as  f o r each i n d i v i d u a l day s e l e c t e d a r e - t a b u l a P t h e mean f r e q u e n c y o f e a c h Pc3 b a n d observed.  TABLE K  0 0 0  1 1 1 1 1 1 1 1 1 1 1  1  17 Nov 18 Nov  25 Oct 20 Oct 19 Nov  3  P  4  0  67  X 1_ °  1_  o 1_  +  0  67  1  1_  +  1_  67  1_  67  67 67  25 Mar 67 20 J u n e 67 2 Mar  67  24 Oct  67  21 J u n e 67 6 Nov 67 17 Mar 9 May  2  °+ X  31 J u l y 67  10 F e b  (TV  K  Date  0  OF  DEPENDENC  o  67 67  °  +  0  0  ° 1_  0  0  1 1_+  °+ I  0 0o 0  °  1  +  + 1 o  DIURNAL  6  5  °  1_  °  1_  -r +  2_  1 o  X X 1 o  X X 2_ 1  +  1_ 1, T  o 1_ 2  1  i ~r  o 2_  2  X 2_  1 0  1_  °+ °  1_ 1_ 1_ 1_ 1+ 1+ 1o 1  1  +  o  °  X 1  +  + +  +  l  °  +  +  °o 0 0  VARIA TION  CF  8  '3 (mHs) (n iHz)  1  3  2  Pc3  +  0 0  0 0 i  o  o  +  °+  1_  1  1_  °+  1  1_  No  °  0,  -r  Type  J  1_  i,  Pc 3  3o  32  X  3_  30  X  29  X  30  X  30  X  T  o  X 6  1o o 1 0  _  6~ +  30  X  o 1_  32  X  0  1_  1_  1_  8_  30  X  2_  1_,_  1_  2_  35  X  X  1  1  1_  8~ + 9_  32  X  32  X  23  X  32  X  37  X  0  1  °  °  V  °  +  +  o,  IV.1  O  X X 1_ X X X 1+  1  o  2_  1+ 1 + 1,  1_  1  1  o 0  T  0  %  X 10_  l l l l l l l l l l l l l l  4  8 8 00  X  -3-  00  OJ  00  X  x  x  -  OO  CM  X l/h  H  -=3"  OO  OO  X  00  v.  Q) r o a,  OJ  X  N  00  X  OO  X  OJ  OO  X  X  oo o j oo oo O J X X X X X  X  o  in o  h  -rt  -3"  IIO -cj-  o  N 0")  m  h  OO  00  OO  t- vo  r-i  r-\  r-\  in oo  r-\  vo  I  I  +  rH  I  OJ  O OJ OJ  I  I  O  r—I  o  I  OJ  +  OJ  00  OJ  +  I  OJ I  00  J  o  OJ  -  OO  OJ  X  X  OO  X  oo oo X X  00  rH  rH  r—I  I  +  OJ  OJ  I  H  o  OO  vo  vo  o •p  -p a,  -P  50  P  CO  o  <  -=3"  m  00  OJ  ro  a>  OJ  a,  O  vo  + 00  I  +  OJ  00  OJ  vo  VD  > o  <  OJ  VD H  oo  OJ  OJ  OJ  rH  OJ  X  in  OJ  o  oo  oo  00 o -=1- -=3-  H  O  O  1  O  OJ  00  + OJ  +  OJ  o  o  O  oo  +  I  OJ  o  o  + o oo oo  o  +  +  oo  VO  -3-  I  I  I  c-  ,Q  ro  r-  CD  > o  +i  OO  OJ OJ  ro  OO  OO  oo  OJ  OJ  1  1  1  1  00  OO  00  oo  oo  m  in  VD  O 00  -3-+  in  vo  ^  VD  VD  • + m  VD  m  OO  in  OJ  +  -=r-  +  00  I  Ln  + o  -3-  +  +  I  oo oo  o  +  +  I  OJ  o  00  U  m  OJ  VD  vo  0VO  VD VO  o  o  o  o  p  p  P  P  CO  CD  ro  OJ  CO OJ  t-  CO  VO OJ  O OJ  O OO  oo  oo  -3-  -3-  in  vo  cu  CD  1  oo  CD  1  oo  CD  vo  +  o . o  -=3-  t—  CO  vo  o  O I OO -=j-  VO  u  VD OJ  co  o  VO  o  rH  OJ  o  VD  oo  +  .=t  00 CO  o  I  +  + o oo oo  vo  p  o  -=t  o + oo OJ  VO  CD  o  -=}-  oo  o OJ  in  -=r-  o OJ  I  + +  + o oo oo  I  VD  O OJ  o  o  oo  I  m  vo  oo  OJ  oo  O I OJ OO  O  oo ^  +  r-  oo . 3 -+  oo  OJ  o  o  oo  O OJ  00  oo  in  OJ  00  oo  OO  o  o  o OO  vo  OJ  -^3"  o OJ  o  o  I  iH  I  OJ  H  O  OJ  OJ  + CO  | — I OJ  I  OO  oo  00  X  i n co oo  rH  X  X  IA  OJ  hO  OJ  OJ  X  co vo  I  +  OJ  X  in vo  .^t-  oo  o  OJ  X  oo in  OJ  OO  00  OJ  X  in in  I  00  OO  X  OJ  X  in s vo  OO  O OO  OJ  X  -3-  O  OJ  + + O O O OJ OJ 00 00 OO  OJ  oo  r-i  + O O 00 i - | OO 00 + O 00 OJ OJ  00  -=3"  o i + o o oo m m t — co  CO  OJ  X  0-  -P OJ  89  It during  has been n o t i c e d  extremely  quiet  that  no Pc3 a c t i v i t y  conditions.  of  those  extremely  quiet  K  index  has been p e r s i s t e n t  July  days where  31,  the zero  throughout  i s observed  1967 value  i s one of the  most o f t h e t w e n t y -  P four  hours.  Such e x t r e m e l y  quiet  conditions  occur  only  rarely. As of  the value  t h e Pc3 band  least  of  also  f o r the value  frequency  increases,  increases. K  l e s s than  i sdirectly  t h e mean  frequency  I t has been found or equal  proportional  to K  t o 4,  .  This  that  at  t h e mean agrees  with  P what h a s been demonstrate Pc3  reported  by Nagata  t h e dependence o f t h e d a i l y  o n 2. K p , a n e x a m p l e  continuous  and F u k u n i s h i  and  one-half  12,  1967.  day period A graph  against  I V . 2a w h e r e a  covering  f r o m D e c e m b e r 4,  of 2 K  To  mean f r e q u e n c y o f  i s shown i n F i g .  sonagram h a s been d i s p l a y e d  (1968).  1967  Universal  a  seven  t o December Time h a s been  tr  plotted  i n the upper  portion  o f the.same  d i a g r a m . 2.K  i s  P useful the As  long  IV.2a,  appears  December 6 c a u s i n g to increase.  the f o l l o w i n g three  reverse The  f o r i tprovides  by F i g .  boundary  pulsation in  case  a rough  i n d i c a t i o n of  r a n g e movement o f t h e m a g n e t o s p h e r i c  suggested  spheric to  i n this  trend  variation  inward  movement o f t h e m a g n e t o -  t o be t a k i n g  the eigen  place  frequency  The c o n d i t i o n  of the daily  f r o m December  steady  assumes a  r a p i d l y f r o m December 9 mean p e r i o d  4  of magnetic  becomes f a i r l y  days and e v e n t u a l l y  and expands  boundary.  o f Pc3  onward.  follows  9 0  c l o s e l y the v a r i a t i o n of the value  of SK^.  The t y p e  d i u r n a l v a r i a t i o n of Pc3 frequency  a l s o a p p e a r s t o change  w i t h changing l e v e l of magnetic d i s t u r b a n c e . that take and  place  afternoon  ranging  The  from the normal type  of  changes  with morning  s e p a r a t i o n o f December 7 t o t h e d i f f u s e d  i n v e r t e d U - t y p e t h a t a p p e a r s o n December 1 0 c o r r e s p o n d  to  moderately disturbed to quiet c o n d i t i o n s . The m u l t i - p e r i o d i c i t y o f P c 3 d e s c r i b e d chapter  p l a y s an i m p o r t a n t  dependence o f f r e q u e n c y presented  i n this  i n the l a s t  r o l e i n our study  o f t h e Kp  o f m a g n e t i c p u l s a t i o n t o be  section.  I t has been observed a t R a l s t o n  t h a t f o r Kp g r e a t e r t h a n o r e q u a l c h a r a c t e r i s t i c s of Pc3 b e g i n  t o 2,  the  multi-band  t o be s i g n i f i c a n t .  The  result  of t h i s o b s e r v a t i o n has been t a b u l a t e d i n T a b l e I V . 1 . frequencies  f ^ and  s o n a g r a m s show c l e a r l y value  obtained  by s c a l i n g t h e  contoured  an upward i n c r e a s e t r e n d as t h e  o f Kp i n c r e a s e s .  S c a l i n g o f t h e mean f r e q u e n c y  a s o n a g r a m h a s b e e n f o u n d o f t e n t o be d i f f i c u l t when o v e r l a p b e t w e e n two P c 3 b a n d s h a s t a k e n c a s e s one o f t h e two b a n d s o c c u r s o n l y and i t may begins  The  be o f s u c h l o w e r  t o doubt i t s r e a l  from  particularly  place.  I n some  over a very b r i e f  interval  signal strength that  one  existence.  The f2| b a n d i s u s u a l l y much w e a k e r i n s i g n a l  strength  t h a n t h e f ^ band u n d e r m o d e r a t e l y d i s t u r b e d c o n d i t i o n s  (Kp<3)  As t h e m a g n e t o s p h e r i c c o n d i t i o n s become more d i s t u r b e d , t h e f ^ band becomes s t r o n g e r .  For the value  o f Kp g r e a t e r  4, t h e s i g n a l s t r e n g t h o f t h e f ^ band i s much g r e a t e r the f ^ band.  than than  91  Tnere I s a l s o a n o t h e r band o f P c 3 o b s e r v e d under moderately disturbed conditions.  I t i s t h e 25 mHz P c 3  b a n d t h a t was r e p o r t e d i n t h e l a s t  chapter (Table  III.l).  U n l i k e t h e o t h e r two b a n d s , t h e f r e q u e n c y o f t h e f d o e s n o t show c l e a r K i n t e n s i t y of the f K  2  2  band  d e p e n d e n c e , a l t h o u g h t h e maximum  band h a s been f o u n d  t o o c c u r when  i s a t a p p r o x i m a t e l y 2. A g r a p h o f Kp d e p e n d e n c e o f t h e mean  o b s e r v e d a t R a l s t o n has been p l o t t e d  frequency  f o r a l l t h r e e bands  o f P c 3 , namely f g , f g , and f ^ ( F i g . I V . 2 b ) .  A  similar  r e l a t i o n s h i p r e p o r t e d by N a g a t a and F u k u n i s h i from K a k i o k a = 2b?o), a n d B o l s h a k o v a f r o m B o r o k (0 = 53?0) h a s a l s o b e e n p l o t t e d o n t h e same d i a g r a m .  f o r comparison.  I t i s most I n t e r e s t i n g t o f i n d  that of a l l the  g r a p h s p l o t t e d i n F i g . IV.3b, o n l y t h e f g band o b s e r v e d a t Ralston i s approximately p a r a l l e l  t o t h e 15 mHz P c 4 b a n d ,  a n d n o t t h e 35 mHz P c 3 b a n d r e p o r t e d b y N a g a t a a n d Fukunishi.  That i s t o s a y , t h e f g band o f p u l s a t i o n  o b s e r v e d a t R a l s t o n b e h a v e s t h e same way a s t h e P c 4 a t K a k i o k a would behave u n d e r d i f f e r e n t conditions.  A similar  magnetospheric  t r e n d has a l s o been o b s e r v e d f o r  t h e P c 3 band r e c o r d e d by. B o l s h a k o v a when t h e v a l u e o f K^ is  s m a l l e r than 3 (see F i g . IV.3b).  T h i s f i n d i n g has  p r o f o u n d i m p l i c a t i o n a s i t may r e v e a l l o c a t i o n s w i t h i n t h e magnetosphere where t h e d i f f e r e n t bands o f P c 3 o b s e r v e d at R a l s t o n c o u l d have  originated.  92  It f  m  has been n o t i c e d a l s o  I s t o be p l o t t e d  value  t o t h e Pc3 c u r v e  In  the last  variation  into  and Xg used  i n Table  individual  event  frequency dition  i s both  i n the last  chapter are  the quality  w i t h r e s p e c t t o each  appears  IV.1, the d i u r n a l  The d e s i g n a t i o n s X - ^  chapter.  IV.1 t o s i g n i f y  (Type  and F u k u n i s h i .  according to the c l a s s i f i c a t i o n  III.3  I t i s evident from  t o be  f o r steady days has been  i n the last  i n Table  U-type  appear  three columns of Table  a g a i n used  inverted  would  g i v e n by Nagata  four types  scheme p r o p o s e d  type.  curve  o f Pc3 f r e q u e n c y  classified  of  t h e two f ^ and f ^ c u r v e s f o r e a c h  o f Kp, t h e r e s u l t a n t  parallel  Xg  from  t h a t i f t h e mean v a l u e  the Table  of  particular  each  basic  that the diffused  3 ) of diurnal  variation  o f Pc3  t o o c c u r when t h e p l a n e t a r y m a g n e t i c  q u i e t and s t e a d y  con-  ( K •< 2 ) , w h e r e a s o n e o f  P or  a mixture  moderately  of the other types  i s t o be o b s e r v e d  d i s t u r b e d c o n d i t i o n s (2<  K C  4).  during  For  P Kp>  k,  the condition  variation To  becomes so d i s t u r b e d t h a t t h e d i u r n a l  o f Pc3 f r e q u e n c y further  c o u l d n o t be s i m p l y  illustrate  Table  e x a m p l e s a r e g i v e n i n F i g . IV.2c example has been g i v e n f o r each  classified.  IV.1, p a r t i c u l a r  t o F i g . IV.2g. different  One  value of  from  0 t o 4. The Fig.  IV.2c  as d i f f u s e d  g e n e r a l appearance and F i g . IV.2d U-type d i u r n a l  of the examples g i v e n i n  i s very  similar.  variation.  They b o t h  behave  93  The  example g i v e n i n P i g . IV.2e f o r Kp = 2 d i s p l a y s  c l e a r multi-band s t r u c t u r e with s p i k e - l i k e d i s c r e t e appearance.  The  d i s c r e t e appearance i s a f e a t u r e common  to a l l cases under moderately q u i e t c o n d i t i o n s (K between 2 and  3)  or when the c o n d i t i o n i s q u i e t  is  and  unsteady (see S e c t i o n I I I . 4 ) . Tne March 27 event shown i n F i g . IV.2f f o r K shows a normal type of d i u r n a l v a r i a t i o n of The  s e p a r a t i o n between the morning and  =  p  3  frequency.  afternoon  type of  P c 3 i s not at a l l c l e a r on the o r d i n a r y sonagram because the two  bands overlap around and a f t e r 1400  confusion.  L.T.  causing  However, the contoured sonagram d i s p l a y e d i n  the lower p o r t i o n of the diagram r e v e a l s the two-band nature  of t h i s p a r t i c u l a r event. Another example of the normal type of d a i l y  v a r i a t i o n of P c 3 frequency  which has morning and  afternoon  s e p a r a t i o n i s c l e a r l y i l l u s t r a t e d i n F i g . IV.2g.  However,  care should be taken i f one  i s to compare t h i s example with  the example g i v e n i n F i g . I I I . 3 a In the l a s t U n l i k e the event of October 18,  1967  chapter.  which occurred  under  moderately q u i e t c o n d i t i o n s , the event shown i n F i g . IV.2g took p l a c e when the magnetic c o n d i t i o n was Further,  the December 26,  1966  reasonably  event d i s p l a y s double p e r i o d i -  c i t y i n the morning as w e l l as i n the afternoon, that observed on October 18,  disturbed.  1967.  contrary  to  40  ,  30-  20  -  10 0  J  1  1  FIG.IV.2a  1  1  ZKp  1  1  1  1  1  Dependence of the  1  1  Pc3  1  -+  Mean  Frequency  F I G . IV. 2 b  Kp  Dependence  Ralston  at  4> = 5 8 . 8  FIG.IV.2c  RALSTON X  b  NOVEMBER 18 1967 Kp = 0  FKS.IV.2d  RALSTON X  b  May 1 0 . 1 9 6 7  Kp = 1  FG.IV.2e  RALSTON X  b  October 5, 1967  Kp - 2  U.T.  6  —  I  L.T.  23  8  .  [  K>  • I  .  12  14  I  • |  16  •  I  18  •  20  I  • I  11  1  TVP« • •» SOMAQHAM •  FC.IV.2f  22  13  KAY «L*CTIIIC CO.  RALSTON Xb  00  • 1 • I 15  2  4  • I  • I  19  21  17  PIN* ITOOK. H. J.  March 27,1967  Kp - 3  23  1  FIG. IV. 2g  RALSTON X  b  December 26, 1966  Kp = 4  101  IV.3  SUDDEN ENHANCEMENT OF Dependence o f the  Kp  index  has  These a u t h o r s  amplitude  Munch, 1964;  i n t h e Kp  dependence of the a t R a l s t o n . The  section. 2 Kp,  a s may  But  be  t h e Kp  could offer  corresponding  Kp  Mainstone,  amplitude  of Pc3  indices.  A similar  1963).  oscillation trend  amplitude  o f Pc3  oscillation  i n the  illustrated index,  level  case the  value  of  general disturbance  s h o r t r a n g e movement i n t h e  index would not  i n c r e a s e d from the  usually  amplitude  afternoon has  been  and  y e t , no  result  of  in a  Pc3.  of 1 to the value  significant  index  of 3 i n the  i n c r e a s e i n Pc3  activity  observed.  However, t h e r e enhancement o f Pc3 following a similar examples are Fig.  value  the  level  An e x a m p l e i s shown i n F i g . TV.3a where t h e Kp has  last  o f l o n g r a n g e movement o f the  change o f the  magnetic  i n F i g . IV.2a of the  or i n t h i s  indication  of  the  1959;  i s generally  w i t h i n t h e m a g n e t o s p h e r e ; any of the  and  (Maple,  of Pc3  m a g n e t o s p h e r i c b o u n d a r y and  value  p u l s a t i o n on  amplitude  usually increases with a rise disturbance  of Pc3  McNicol  observed t h a t the  increases with a rise  evident  ACTIVITY  b e e n r e p o r t e d by many a u t h o r s  C a m p b e l l , 1959;  o f Kp  Pc3  are  a few  a c t i v i t y has rise  i n the  independently  occasions  when s u d d e n  been observed t o t a k e value  o f t h e K^  index.  d i s p l a y e d i n F i g . IV.3b  IV.3c t o d e m o n s t r a t e t h e w o r k i n g o f the  place  and  phenomenon.  Two  102  In  F i g . I V . 3 b , an a b r u p t  I n c r e a s e o f Pc3 a m p l i t u d e ,  Indicated  by an i n c r e a s e i n d a r k n e s s  o f t h e sonagram, has been  at  May 21, 1967 w h i c h i s t h e t i m e  approximately  within from  2100 U.T.  the three hour i n t e r v a l  a value of 1  Q  t o 3+.  when t h e K  In  F i g . IV.3c,  o f Pc3 a c t i v i t y is  i n d e x has  risen  N o t i c e a l s o t h a t t h e sudden  enhancement o f m i c r o p u l s a t i o n a c t i v i t y Pc3 b a n d o n l y (25-60 mHz  p  observed  i n the case  another  takes place i n the  o f t h e May  21 e v e n t ) .  example o f sudden enhancement  corresponding  t o an i n c r e a s e i n t h e K  shown where two P c 3 b a n d s h a v e b e e n i n i t i a t e d .  t h a t an e n h a n c e m e n t o f P c 4 a c t i v i t y  occurs p r i o r  p  index  Notice to the  enhancement o f b o t h o f t h e Pc3 b a n d s w h i c h t a k e s p l a c e a t approximately  1830 U.T.  Two  s o n a g r a m b e f o r e and a t 1723  calibration U.T.  m a r k s a p p e a r on t h e  103  F I G . IV.3o  RALSTON  x  K  AUGUST  9 , 1967  104  U T 6 8 | , | L.T. 2 3 1  ,  10 [ 3  , 5  12 |  •  1 4 1 6 1 8 2 0 2 2 [ I • 1 • I • I 7 9 11 1 3 1 5 11ft. m, «a soNAaitAM •  F I O . IV. 3b  RALSTON SUDDEN  KAT KI_ICTKIC C O .  X  b  '  rms. B R O C K  0 2 4 6 8 I ' I ' l l 17 1 9 2 1 2 3 1 H. J.  M A Y 22. 1969  ENHANCEMENT  O F Pc 3  105  FIG. IV.3c  RALSTON SUDDEN  Xb  AUGUST  ENHANCEMENT  OF  23,  1967  Pc3  A  Pc4  106  IV.4  DISCUSSION Based  Snyder  on data o b t a i n e d on board  e t a l (1963)  demonstrating  have  the linear  derived  M a r i n e r 2,  an e m p i r i c a l e x p r e s s i o n  relationship  between  X K  and t h e  P velocity derived  of the solar  t h e IMP-1 o b s e r v a t i o n  from  approximately it  linear  relation  i sn o t i n c o n c e i v a b l e  s p h e r e more  compressed  ponding  t o an i n c r e a s e  shorter  period  indicated 1966), of  f o r t h e case  theoretical  is  because  corres-  may r e s u l t  i na  (Hirasawa e t a l ,  and t h e f r e q u e n c y  has been  anticipated.  h a s so f a r c o n f i r m e d  i f the existence  mode  inside  one would  different  more  wind,  eigen o s c i l l a t i o n as  between K  pulsation  o r magneto-  this  of themulti-band  Pc3 i s i n d e e d due t o t h e e i g e n o s c i l l a t i o n o f  resonators both  change  indices,  Since  speculation.  the m o d i f i e d A l f v e n  two  solar  o f Pc5 o s c i l l a t i o n  observation  Further,  matrough,  i nthe K  have  there i s an  t h e plasmasphere  by t h e stronger  correlation  Pc type o f magnetic  Experimental  that  that  also  between V and K .  of hydromagnetic  a direct  structured  W i l c o x e t a l (1964)  wind.  s e t up i n t h e e a r t h  t h e plasmasphere  and I n t h e p l a s -  expect the eigen o s c i l l a t i o n s  r e s o n a t o r s t o respond  i nmagnetospheric susceptible  magnetic  differently  conditions.  density,  t oany  As t h e p l a s m a t r o u g h  t o the compression  o f it'slow p a r t i c l e  i n the  of the solar  o n e may  wind  anticipate  107  t h a t  t h e  o r i g i n a t i n g  m o r e  s e n s i t i v e  Pc3  t o  a n y  c o u n t e r p a r t  i n  l e a d s  b e l i e v e  u s  t o  o r i g i n a t e s w h e r e a s s p h e r e  i n  t h e  e t t h e  i s  f ^  t h e  t h e  t h a n  K  i n d e x  p  T h e  f ^  o f  I f  a b o v e  s u b - b a n d o u t s i d e  a l o n g  o f  t h i s  d i m e n s i o n  o f  t h e  p l a s m a p a u s e . t u r n  A s  t h e  b e i t s  c o n s i d e r a t i o n  o f  t h e  p u l s a t i o n  Pc3  p l a s m a p a u s e  i n s i d e  t h e  t h e  c u r v e  i s  t h e  f i e l d  e i g e n  p l a s m a -  o f  c o m p r e s s i o n  l o g i c a l  t o  e x p e c t  f r e q u e n c y m a g n e t i c  o f  ( K p ~ 3 ) j  t h e  b y  c l o s e t h e f ^  t h e  t h e  i s  i n s i d e  (f-^)  Pc4  b a n d  b a n d  o f  Pc3  b a n d  i s  f o u n d  t o  b e t w e e n a n d  u n d e r  t h e  w a v e  r e f l e c t  t h e  . t h e  t h e  b y  t h e a n d  d i f f e r e n t  s t r e a m s ,  c o r r e l a t i o n  o f  p l a s m a p a u s e ,  s u b j e c t  s o l a r  t h a t  p l a s m a p a u s e ,  b o u n d e d  t h e  i n  N a g a t a  s p e c u l a t i o n  t h e  w h i c h  c h a n g e  b y  h y d r o m a g n e t i c  a t  o f  s h o w n  i t  i s  t h e  c h a n g e  c h a n g e  d i f f e r e n t  o n l y  o f  o f t h e  l e v e l s  o f  a c t i v i t y .  A l s o , t h e  o f  a  g i v e n  o s c i l l a t i o n w o u l d  d i m e n s i o n s  d e g r e e s  o u r f r o m  b y  l i n e  p l a s m a s p h e r e t h e  f o r  c a u s e d  f ^  c u r v e  Pc4  o r i g i n a t e d  p l a s m a s p h e r e ,  f r e q u e n c y  t h e  t h a t  s u p p o r t  Pc3  Pc4  f a c t  t o  f u r t h e r  f r e q u e n c y  w h e n  w o u l d  o r i g i n a t e s  p a r a l l e l  s u b - b a n d  p r o p a g a t i n g  t h e  o f  p l a s m a t r o u g h  s u b - b a n d  p r o v i d e s  p l a s m a p a u s e .  i n  t h a t  o b s e r v a t i o n a l  IV.2b a l  c h a n g e  p l a s m a t r o u g h  p l a s m a s p h e r e .  t h e  f ^  t h e  . T h e  F i g .  t h e  i n  t h e  f ^  m a g n e t i c  c o n d i t i o n  t h a t  w h e n  p l a s m a p a u s e .  i s , O n  t h e  i s  R a l s t o n  o t h e r  h a n d ,  t o  b e  s i g n i f i c a n t  r e a s o n a b l y i s  w e l l w h e n  d i s t u r b e d  o u t s i d e t h e  o n l y  t h e  m a g n e t i c  c o n d i t i o n  108  i s q u i e t R a l s t o n would be i n s i d e the plasmasphere and only dominating  the  p u l s a t i o n observed would be i n the i\  band.  T h i s o b s e r v a t i o n a g a i n i s c o n s i s t e n t w i t h our proposed model. The  f  band of P c 3 d e s c r i b e d i n S e c t i o n I I I . 2 of  the l a s t c h a p t e r has not demonstrated c l e a r K^-dependence. T h i s p r o p e r t y may  be v i t a l i n our u l t i m a t e  of the exact n a t u r e The  of the f  present  understanding  band of P c 3 .  author b e l i e v e s , as many o t h e r s  do,  t h a t a Kp index i s a measure of p o l a r substorm a c t i v i t y . I t s enhancement i s thought to accompany an i n j e c t i o n of p a r t i c l e s i n t o the magnetosphere which cause an i n s t a b i l i t y of the plasmapause, g i v i n g r i s e to a o s c i l l a t i o n i n the d a y s i d e  hydrornagnetic  magnetosphere.  Thus, an enhancement of P c 3 a c t i v i t y may be t a k i n g p l a c e . this possibility.  The The  example g i v e n i n P i g . I V . 3 c suggests sudden enhancement of  activity  f o r the August 2 3 event took p l a c e f i r s t i n the frequency  then  Pc4  range which i s then f o l l o w e d by an e x c i t a t i o n  of the two P c 3 bands.  T h i s may  suggest t h a t t h i s k i n d of  sudden enhancement begins w i t h e x c i t a t i o n of the plasmapause. Obviously,  the r e s u l t so f a r o b t a i n e d  i s not  sufficient  f o r us to draw any c o n c l u s i o n s , and f u t u r e r e s e a r c h l o o k i n t o the p o s s i b i l i t y of s i m u l t a n e o u s  should  observations  109  b e i n g made a t two  stations approximately  geomagnetic l o n g i t u d e .  l8o° a p a r t i n  110  CHAPTER  V  COMPARATIVE STUDIES OF Pc3 IN HIGH AND MID-LATITUDES  V.l  INTRODUCTION In order t o understand the o r i g i n of micropul-  s a t i o n , i t i s o f prime importance t o determine a c c u r a t e l y any r e g u l a r i t i e s t h a t govern the changes o f m i c r o p u l s a t i o n amplitude and p e r i o d w i t h l a t i t u d e , and the d i s t r i b u t i o n of p u l s a t i o n s observed on the e a r t h ' s s u r f a c e . a tremendous researchers  Although  amount o f work has been done by numerous on t h i s s u b j e c t s i n c e t h e IGY, and u n d o u b t e d l y  g r e a t advances have been made i n the p a s t decade t h r o u g h use of b e t t e r s p e c t r a l a n a l y s i n g t e c h n i q u e s ,  there i s not  yet a c o n s i s t e n t p i c t u r e t h a t c o u l d e x p l a i n the apparent controversy  among d i f f e r e n t r e s u l t s r e p o r t e d by d i f f e r e n t  workers. T h e o r e t i c a l a t t e m p t s t o f o r m u l a t e the n a t u r e o f a l a t i t u d e dependence, of the magnetosphere, and v/atanabe  based on hydromagnetic  resonances  were made by Dungey (1954) and Kato  (1956a). Dungey's c a l c u l a t i o n s have been  extended by Westphal and Jacobs (1962) t o i n c l u d e more r e c e n t knowledge  o f the magnetosphere.  Each o f these and  some l a t e r c a l c u l a t i o n s were based on c e r t a i n assumptions about the d e n s i t y d i s t r i b u t i o n i n the magnetosphere.  These  c a l c u l a t i o n s have a l l p r e d i c t e d a s t e a d y i n c r e a s e i n t h e p e r i o d o f m i c r o p u l s a t i o n w i t h an i n c r e a s e i n geomagnetic latitude.  Ill  Indeed, e a r l i e r various  experimental observations  a u t h o r s have a l s o p r o v i d e d  theoretical  prediction that  the  support  periods  types of c o n t i n u o u s p u l s a t i o n i n c r e a s e in  latitude.  world,  studying  O b a y a s h i and  systematic (j) and  By  concluded  to cos  the  and  Zybin  most s t a b l e p u l s a t i o n s the  l a t i t u d e range  the  result  from data daytime  earth,  events that  More r e c e n t  observations  planned to  (i960)  with  reported  (1966),  and the  They have r e p o r t e d  periods  the  the  periods  five  as  created  found  of  stations  well  not  assume  the within  However,  derived as f r o m  hold  for  today. more c o n f u s i o n  than  I n v e s t i g a t i o n s on  from three  Troitskaya  (1967) f a i l e d  instances  (1961)  results,  Heitzler  dependence o f P c 3  the  stations  H e r r o n and  that  the  the  p e r i o d made by Duncan  same d a t a  notably  a c l e a r p i c t u r e of  as  Pc3  the  period with l a t i t u d e  29°S - 52°S gave c o n t r a d i c t o r y  authors,  Stuart  the  we  resolve.  dependence o f t h e  other  latitude.  often  i t may  daytime Pc3  U s h e r and  longer  around  J a c o b s was  nighttime and  4  increase  ( T r o i t s k a y a , 1967) .  O b a y a s h i and  s i d e of the  l a t i t u d e range  obtain  by  from the  Ellis  while  at each of the  obtained  latitude  in  an  and  i s inversely proportional  upon s t u d y i n g  23°N-»64°N  reported  they o r i g i n a l l y  and  period  3*  A s i m i l a r c o r r e l a t i o n v/ith l a t i t u d e was  by B o l s h a k o v a  purely  (1958) f i r s t  of m i c r o p u l s a t i o n  that  of Pc2, with  by  the  simultaneous records  Jacobs  increase  for  made  (1966), to  period  on  when somewhat  are  observed  at h i g h  l a t i t u d e occur  instances  when t h e  reverse  applies.  just  as  112  S c r u t i n y of m i c r o p u l s a t i o n events  simultaneously  recorded on r a p i d - r u n magnetograms a t Great Whale R i v e r (0 = 6 6 . 6 ° ,  e -  347.4°),  and R a l s t o n (0 = 5 3 . 0 ° ,  McGlll  (<b = 5 7 . 0 ° ,  0 -  354.3°),  9 = 3 0 5 . 5 ° ) also i n d i c a t e that i n  some i n s t a n c e s t h e p e r i o d o f P c 3 may be observed  t o be  l o n g e r a t Great Whale, w h i l e i n o t h e r i n s t a n c e s t h e p e r i o d of P c 3 i s t h e same f o r a l l s t a t i o n s .  On some o c c a s i o n s  the p e r i o d of P c ' s i n the h i g h l a t i t u d e has even been found t o be s h o r t e r than t h a t observed  i n the m i d - l a t i t u d e .  We s h a l l d e s c r i b e these r e s u l t s i n S e c t i o n V . 2 as a p r e l u d e to f u r t h e r i n v e s t i g a t i o n t o be made i n t h e l a t e r s e c t i o n s . I t has been r e c o g n i s e d t h a t two main causes may be responsible f o r the apparently c o n t r a d i c t o r y r e s u l t s o b t a i n e d from e x p e r i m e n t a l o b s e r v a t i o n s .  The l a c k of  s u f f i c i e n t h i g h q u a l i t y data may be t a k e n as one o f the p r i n c i p a l reasons.  Indeed, i t has always been r e a l i z e d  t h a t u n l e s s data o b t a i n e d from d i f f e r e n t s t a t i o n s are recorded  s i m u l t a n e o u s l y w i t h i d e n t i c a l equipment and w i t h  s t a n d a r d i z e d t e c h n i q u e s and c a l i b r a t i o n s , i t would be v e r y d i f f i c u l t f o r one t o compare these d a t a i n an e x a c t manner. Because o f t h e s c a r c i t y of good q u a l i t y data  present-  l y a v a i l a b l e , many r e s e a r c h e r s have t o r e s o r t t o a s t a t i s t i c a l approach as a p r i n c i p a l means t o r e s e a r c h i n the f i e l d . S t a t i s t i c a l a n a l y s e s undoubtedly  have y i e l d e d much i n f o r m a -  t i o n o f v a r i o u s t y p e s of geomagnetic p e r t u r b a t i o n phenomena, yet,  s t a t i s t i c a l r e s u l t s may o f t e n be found t o be v e r y  m i s l e a d i n g , p a r t i c u l a r l y when more t h a n one p a r a m e t e r i s  113  i n v o l v e d i n the study. The second major cause o f t h e apparent i n c o n s i s t e n c y of t h e o b s e r v a t i o n a l r e s u l t s i s t h e p r e s e n t l a c k o f p r e c i s e knowledge  i n other r e l a t e d f i e l d s or i n other related  w i t h i n t h e same f i e l d .  topics  I t s h o u l d be noted t h a t , even i n  the comparison o f s i m u l t a n e o u s e v e n t s , c o r r e l a t i o n s may not always be m e a n i n g f u l .  I n the study of the l a t i t u d e  dependence o f p u l s a t i o n f r e q u e n c y , f o r i n s t a n c e ,  comparison  of any s t a t i s t i c a l l y o b t a i n e d mean p e r i o d s o r f r e q u e n c i e s may be v e r y m i s l e a d i n g i n d e e d where no account has been t a k e n o f magnetic a c t i v i t y , d i u r n a l v a r i a t i o n s , e t c . the l a c k of p r e c i s e knowledge  Thus  of the d i u r n a l behaviour or  K - dependence o f P c 3 a t any s i n g l e s t a t i o n would P hamper r e s e a r c h on i t s l a t i t u d e dependence.  also  The t h r e e main s t a t i o n s t h a t we have chosen f o r comparison a r e s i t u a t e d i n such a p o s i t i o n t h a t Great Whale R i v e r and M c G i l l l i e c l o s e l y on the same geomagnetic m e r i d i a n whereas R a l s t o n and M c G i l l are a t about t h e same geomagnetic latitude.  T h e . t e l l u r i c sonagrams p u b l i s h e d i n High L a t i t u d e  G e o p h y s i c a l Data by t h e G e o p h y s i c a l I n s t i t u t e ,  College,  A l a s k a ((J) = 64.65°N, Q = 256.56°E) over a p e r i o d from J a n u a r y t o March 1967 have a l s o been used f o r comparison. Our p r e s e n t emphasis i s on t h e d e t a i l e d s t u d y of t y p i c a l events selected according t o the c l a s s i f i c a t i o n scheme proposed i n Chapter I I I .  O b s e r v a t i o n s made a t R a l s t o n  are t a k e n as a base f o r comparison w i t h o t h e r s t a t i o n s  114  because of the h i g h q u a l i t y o f i t s tape recorded Examples d i s p l a y e d f o r i l l u s t r a t i v e  data.  purposes are so  s e l e c t e d that o n l y data a v a i l a b l e from the maximum p o s s i b l e number o f s t a t i o n s are used.  Unfortunately  tape recorded  Whale R i v e r are of  data from Great  low n o i s e to s i g n a l r a t i o ,  only very few sufficiently  and no magnetic tape recorded  data  are a v a i l a b l e from M c G i l l , so except f o r the few a v a i l a b l e tape recorded Alaska,  data from Great Whale R i v e r and C o l l e g e ,  comparison can be made only on c h a r t  records.  In S e c t i o n V . 4 the l a t i t u d e dependence o f P c 3 frequency  w i l l be s t u d i e d I n the l i g h t  o f the r e c e n t l y  a c q u i r e d knowledge on the d i u r n a l v a r i a t i o n o f frequency at R a l s t o n (Chapter V.3), last  I I I ) and at Great Whale R i v e r ( S e c t i o n  and a l s o on the K -dependence o f P c 3 r e p o r t e d i n the p  chapter.  I t has been found that some o f the apparent  i n c o n s i s t e n c y i n the p r e v i o u s  as w e l l as i n the present  o b s e r v a t i o n a l r e s u l t s may be r e s o l v e d I n the present under the new p e r s p e c t i v e .  study  T h i s i s to be summarized i n  Section V . 6 . In S e c t i o n V . 5 ,  conjugacy of P c 3 o f both the h i g h  and m i d - l a t i t u d e p a i r (Great Whale-Byrd and M c G i l l - E l g h t s r e s p e c t i v e l y ) has been s t u d i e d . i n d i c a t e that Pc3 i s conjugate d i s t u r b e d magnetic c o n d i t i o n s .  Preliminary  results  i n g e n e r a l except under very  115  V.2  LATITUDE DEPENDENCE OF P c 3 FREQUENCY P r e l i m i n a r y O b s e r v a t i o n s on Rapid-Run Magnetograms S c r u t i n y o f r a p i d - r u n magnetograms ( 3 / 4 i n c h p e r  minute r e c o r d i n g speed) from Great Whale R i v e r , R a l s t o n and M c G i l l has i n d i c a t e d t h a t under d i f f e r e n t c o n d i t i o n s t h e f r e q u e n c y o f t h e Pc type of magnetic p u l s a t i o n a t t h e h i g h l a t i t u d e s t a t i o n may be found t o be h i g h e r t h a n , o r lower than, o r t h e same as, t h e f r e q u e n c y o f t h e p u l s a t i o n a c t i v i t y observed a t t h e m i d - l a t i t u d e s t a t i o n s . these c a s e s has been r e p o r t e d observatories.  Each o f  by o t h e r r e s e a r c h e r s  from  other  However, i t has been observed a t t h e t h r e e  Canadian s t a t i o n s t h a t c e r t a i n r e g u l a r i t i e s c o u l d be found governing the existence  o f each of t h e d i f f e r e n t b e h a v i o u r s .  Some o f t h e p r e l i m i n a r y r e s u l t s o b t a i n e d run magnetograms s i m u l t a n e o u s l y s t a t i o n s i s t o be r e p o r t e d  by study o f r a p i d -  recorded at d i f f e r e n t  i n t h i s s e c t i o n as an i n t r o d u c t i o n  t o deeper i n v e s t i g a t i o n t o be p r e s e n t e d i n the f u t u r e sections. No c l e a r l a t i t u d e dependence of P c 3 f r e q u e n c y has been observed under very q u i e t magnetic c o n d i t i o n s ; t h e f r e q u e n c y o f P c 3 i s comparable at Great Whale, M c G i l l as w e l l as a t R a l s t o n .  I n F i g . V.2a,  frequency with respect  the constancy of Pc3  to different l a t i t u d e s i s i l l u s t r a t e d  where peak t o peak c o r r e l a t i o n i s observed f o r t h a t p a r t i c u l a r P c 3 event s i m u l t a n e o u s l y  o c c u r r i n g a t Great Whale,  1 1 6  R a l s t o n and M c G i l l under v e r y q u i e t magnetic (Kp  -  conditions  0 ). +  As the magnetic c o n d i t i o n becomes more d i s t u r b e d , the  l a t i t u d e dependence of P c 3 f r e q u e n c y becomes n o t i c e a b l e  at Great Whale and M c G i l l , p a r t i c u l a r l y so i n the a f t e r n o o n , but the P c 3 f r e q u e n c y remains comparable  between the two  An example g i v e n i n F i g . V . 2 b  s t a t i o n s i n the morning.  shows a c l e a r l a t i t u d e dependence of f r e q u e n c y of P c 3 where the  event observed at Great Whale ( 2 0 — » 2 5 mHz)  i s of much  lower f r e q u e n c y than t h a t observed a t M c G i l l ( 3 5 —* 4 0 mHz). I t I s v e r y i n t e r e s t i n g t o note t h a t at R a l s t o n b e f o r e 1 8 4 3  U.T.  and a f t e r  approximately 2 0 —  l o 4 6  U.T.,  2 5 mHz  the P c 3 i s observed w i t h  i n f r e q u e n c y comparable  Whale, whereas i n the i n t e r v a l between 1 8 4 3 U.T. the  f r e q u e n c y of Pc3 i s comparable  than a t Great Whale.  t o Great  and 1 8 4 6  to that at M c G i l l  U.T.  rather  I n f a c t , even peak t o peak c o r r e l a t i o n  c o u l d be i d e n t i f i e d f o r the r i g h t p a i r s of s t a t i o n s .  A-  s t a t i s t i c a l average of the P c 3 f r e q u e n c y over each of t h e s e s t a t i o n s would s u r e l y suggest t h a t the mean f r e q u e n c y of Pc3  d e c r e a s e s as l a t i t u d e i n c r e a s e s .  I t i s the a u t h o r ' s  o p i n i o n t h a t such a c o n c l u s i o n i s , t o say the l e a s t , v e r y misleading.  On the o t h e r hand, i f the model p o s t u l a t e d i n  Chapter I I I and r e i n f o r c e d by Chapter IV t h a t t h e r e e x i s t s e i g e n o s c i l l a t i o n i n the P c 3 f r e q u e n c y range i n b o t h the plasmatrough and the plasmasphere  i s t o be a c c e p t e d , the  outcome of the o b s e r v a t i o n made and shown i n F i g . V . 2 b may even be p r e d i c t e d .  I t i s o n l y l o g i c a l t h a t i f Great Whale  117  i s i n the plasmatrough while M c G i l l i s i n the plasmasphere, the frequency o f Pc3 observed at the two s t a t i o n s would be d i f f e r e n t , being h i g h e r case.  at M c G i l l i n t h i s p a r t i c u l a r  Suppose the plasmapause i s at such a p o s i t i o n  r e l a t i v e to R a l s t o n  that R a l s t o n may a t one time be found  i n s i d e the plasmapause and at other time o u t s i d e  the p l a s -  mapause i n the plasmatrough, then the frequency o f Pc3 observed at R a l s t o n would s u r e l y be changed  accordingly.  T h i s i s what has been observed i n F i g . V . 2 b . To p r o v i d e  f u r t h e r support f o r our p o s t u l a t i o n  that eigen o s c i l l a t i o n may e x i s t i n the plasmatrough, the f o l l o w i n g experimental o b s e r v a t i o n  i s considered.  There i s another c l a s s of m i c r o p u l s a t i o n P e l with frequency range from 0 . 2 Hz to 5 Hz. p u l s a t i o n s , appear i n p o l a r r e g i o n s  known as These micro-  ( i n c l u d i n g the a u r o r a l  zones) as w e l l as i n the mid- and l o w - l a t i t u d e s .  In mid-  and l o w - l a t i t u d e s they are more l i k e l y to appear during n i g h t time than d u r i n g the day.  T h i s type of a c t i v i t y i s  known to be a hydromagnetic wave that o r i g i n a t e s i n the plasmatrough s e v e r a l to f o u r t e e n e a r t h ' s r a d i i d i s t a n t and Is propagated to one ( o r more) l i m i t e d area(s) i n the p o l a r r e g i o n along magnetic l i n e s of f o r c e (Jacobs and Watanabe, 1964$ Obayashi, 1964; Wentworth,1966).  I t has been r e a l i z e d  that i f a c o r r e l a t i o n could be found between t h i s type of P e l and the P c 3 , mid  whose i n t e n s i t y i s a l s o g r e a t e r than at  l a t i t u d e s t a t i o n s , then one c o u l d i n f e r that the P c 3  118  observed i n the h i g h l a t i t u d e a l s o o r i g i n a t e d i n the plasmatrough. I t i s w e l l known t h a t P e l r e c o r d e d on  helicorder  c h a r t s r u n n i n g a t a s p e e d o f 3 cm/min o f t e n a p p e a r i n b u n d l e s (pearls).  Furthermore,  i n the daytime  the envelope of the P e l observed  a t G r e a t Whale i s o f t e n f o u n d t o be  20-30 s e c p e r i o d .  I t has been o b s e r v e d f o r t h i s  of  particular  type of P e l t h a t c o r r e l a t i o n between the p e r i o d o f i t s e n v e l o p e s and  the c o r r e s p o n d i n g Pc3 event r e c o r d e d s i m u l -  t a n e o u s l y a t t h e same s t a t i o n i s e x t r e m e l y g o o d ( F i g . V . 2 c ) . T h i s c a n n o t be e x p l a i n e d p u r e l y as a b e a t i n g e f f e c t  because  the. f r e q u e n c y o b s e r v e d i s much l o w e r t h a n t h e b e a t i n g frequency c a l c u l a t e d  t h e o r e t i c a l l y and o b s e r v e d e x p e r i m e n t a l l y  on t h e s o n a g r a m ( w h i c h h a s a b a n d w i d t h . M " = 0.2 T  Beat ~  s  e  c  ) . T h i s may  suggest t h a t Pc3 i s a t  Hz i . e . least  p a r t l y r e s p o n s i b l e f o r the m o d u l a t i o n of the amplitude of Pel.  I f t h i s i s i n d e e d t h e c a s e , t h e P c 3 o b s e r v e d must  o r i g i n a t e o u t s i d e t h e knee boundary.  also  i.82 r AT 0.5 Hz  GW  MG  J  I  I  1  I  I  I  |_  Jj  1845  1850  FIGV.2b X , February 17, 1967 K = 3 b  p  0  1.38 r A T 0.5  HE  0.19^ A T 0.5  Hz  o.i i r AT 0.5  Hx  L-  U.T.  ro O  GREAT WHALE,  AUGUST 22. 1966  Pc I Envelope  GREAT WHALE  FIG V. 2c  X , AUGUST 22. 1966  Pc3 Modulated Pc 1 t-  1  122  V.3  D I U R N A L V A R I A T I O N OF  Pc3  - GREAT WHALE R I V E R  2 t o 4),  =  the  activity  may  be  dividing  the  whole  a  typical  to  the  day  one  A HIGH LATITUDE  to mildly  diurnal  disturbed  variation  roughly c l a s s i f i e d 24  hours.  The  g i v e n by  Jacobs  and  7.5)  L =  conditions  of m i c r o p u l s a t i o n .  into  four  regions  p a t t e r n of  been drawn i n Fig.V.3a  has  STATION  66.6°,  (GEOMAGNETIC (ft =  D u r i n g moderate (K  AT  activity  which  (1965)  Wright  i s  on  similar  f o r Byrd  Station. F r o m 17Q0 0100  U.T.)  positive  L.T.  i s the bay  interesting  dusk  to note  t h e r e has  10  sec  Pc5  20  also  are  7  always  period ( P c 2  of  such  of t h i s  been r e g u l a r and  Pc3)  diagram  dusk type  i s a La  lower  slower  and  speed  P c 2  associated withi t .  auroral  -  3  zone;  which  much p o o r e r  Positive  from  data  alone, One  association  a high -  with  speed  3 event of  i s recorded frequency  portion  recorded  near  the  there  typical  In the upper  o f rnagnetogram  portion  has  P c 2  bay  m i c r o p u l s a t i o n of  being observed.  a typical  Cour type  shown i n t h e  of p o s i t i v e  simultaneously.  there i s a part of  showing  r e g i o n where  p e r i o d i n S e p t e m b e r 19&5 events  to  I t i s extremely  event  i s shown i n F i g . V.3b.  bay  magnetogram there  active.  f o r every  very o f t e n i n the  cases  positive of the  that  i n a t e n day  example  very  ( i . e . 2200 U.T.  T h i s i s the  i s very often observed  bays occur studied  2000 L . T .  region.  i s usually  observed to  to  dusk,  same at  and  event  relatively  response.  The  1 2 3  Pc2 it  - 3 event  shown t a k e s p l a c e f i r s t  i sinteresting  that  a positive  feature period This  that  IPDP  that  this  2208 U.T. a n d  i s t h e v e r y moment  b a y b e g i n s t o be o b s e r v a b l e .  s h o u l d be n o t e d  o f t h e same e v e n t  reminds  called  t o note  around  i s that  after  Another  2 2 4 0 U.T., t h e  begins t o decrease  continuously.  us o f another type o f geomagnetic which  particular  local  decreasing  period.  when o b s e r v e d ,  time  usually  and i s always  However,  IPDP  pulsation  occurs around  identified  this  by i t s  i susually of higher  frequency. In usually is  quiet.  Pc5 w h i c h The  0100  example  on  The o n l y  second  example,  impulsive quiet  that  from  be o b s e r v e d  2100 L.T. t o  This i sthe region occurs.  P c 2 and Pc3 a r e o f t e n  rnicropulsatlon  traces  of shorter  activity  may s o m e t i m e s b e  A  events.  of these  period  (^  above,  typical  found  superimposed  The c o n d i t i o n i s  impulsive  events  10 s e c ) p u l s a t i o n  Identified.  morning  by n e g a t i v e bays.  mentioned  where  A s may b e  region  before or near  dawn  - 0 6 0 0 L . T . o r 0600 U.T. - 1 1 0 0 U.T.) i s a r e g i o n invaded  region i s  i n F i g . V.3b.  type u s u a l l y  i n t h e absence  early  may s t i l l  i s presented i n Fig.V.3d.  although  The  bay, t h e dusk  U.T. t o 0600 U . T . ) .  of the impulsive  i n this  generally  activity  region extends  of a P12 event  these  of positive  has n o t appeared  L.T. (0200  pulsation  seen  t h e absence  t h e r e have  Similar also  to the f i r s t  (C100 L.T.  often  region  been P c 2 and P c 3  events  124  a s s o c i a t e d w i t h e v e r y n e g a t i v e bay t h a t we observed i n this region.  The a m p l i t u d e o f t h e bay a s s o c i a t e d P c 2 - 3  has maximum a t t h e r e c o v e r y stage of t h e bay then e v e n t u a l l y d i e s down towards dawn.  B e f o r e o r a t 0600 L.T., a q u i e t  c o n d i t i o n u s u a l l y p r e v a i l s u n t i l t h e onset o f day time P c 3 activity.  One o f t h e e v e n t s observed i s i l l u s t r a t e d i n  F i g . V.3c where b o t h n e g a t i v e bay and P c 2 and P c 3 (10 —» 20 sec) p u l s a t i o n e v e n t s o c c u r s s i m u l t a n e o u s l y around O650 U.T.  P u l s a t i o n of l o n g e r p e r i o d may o c c a s i o n a l l y be  p r e s e n t i n t h e same event which by I t s e l f i s o f t e n fluctuating i n period.  N o t i c e a l s o t h a t t h e i n t e n s i t y of  the m i c r o p u l s a t i o n event has been s i g n i f i c a n t l y  enhanced  o n l y a f t e r t h e bay e n t e r s i t s r e c o v e r y phase a t around 0725 U.T. and then d i e s down toward dawn. of bay a c t i v i t y ,  I n t h e absence  a longer p e r i o d Pc3 w i t h s m a l l e r amplitude  i s u s u a l l y detected with or without Pc5 occurrence. The day r e g i o n (0600 L.T. t o 1700 L.T.) i s v e r y a c t i v e i n continuous p u l s a t i o n events w i t h frequency ranging from 25 Hz t o 70 Hz. The f r e q u e n c y i s u s u a l l y a t i t s h i g h e s t j u s t a f t e r dawn and a t i t s l o w e s t I n t h e a f t e r n o o n . Such a change i n f r e q u e n c y does n o t seem t o t a k e p l a c e continuously.  The daytime P c 3 appears t o be v e r y s e n s i t i v e  to t h e change i n • t h e dimension o f t h e magnetosphere.  This  e f f e c t i s manifested i n the frequency f l u c t u a t i o n o f t e n observed b e f o r e and around l o c a l noon.  P c 3 events are  125  g e n e r a l l y a l i t t l e more r e g u l a r between 0700 L.T. 0900 L.T.  and  when t h e r e seems t o be a maximum i n i n t e n s i t y ,  c o n t i n u i t y and r e g u l a r i t y of p e r i o d . i s o f t e n found around 1400 L.T.  A secondary maximum  or '1500 L.T.  In f a c t ,  cases of v e r y r e g u l a r Pc2 of 10 t o 20 sec p e r i o d have been found on many o c c a s i o n s i n the a f t e r n o o n (1300 i n s t e a d of l o n g e r p e r i o d P c s 1  (the August 19,  i s one of the t y p i c a l examples).  t o 1600 1966  L.T.)  event  A l s o , i t does not seem  t h a t t h e r e i s a d e f i n i t e boundary between Pc2 and P c 3 as suggested by the IAGA committee,  1964.  I n g e n e r a l , the  f r e q u e n c y of Pc2 - 3 i n the h i g h l a t i t u d e s f l u c t u a t e s throughout the day except under v e r y q u i e t c o n d i t i o n s . At t i m e s when the geomagnetic to be at i t s minimum ( K  p  = 0 ->1),  d i s t u r b a n c e i s found  very regular Pc3 - 4  p u l s a t i o n i s o f t e n observed f o r most of the day 1700 L . T . ) .  (0300 t o  D i u r n a l v a r i a t i o n i n f r e q u e n c y does not seem  to be v e r y s i g n i f i c a n t .  The i n t e n s i t y of these P c 3 - 4  p u l s a t i o n s appears t o be at i t s maximum i n the l o c a l morning r  and then d e c r e a s e s towards a f t e r n o o n .  jver:t he2 been reproduced i n ? i g . 7 . 3 e  A typical  where n e a r l y peek  to peak c o r r e l a t i o n has been shown t o o c c u r between highland m i d - l a t i t u d e s t a t i o n s f o r these t y p e s of P c 3 - 4 activities. in.'i.v  I  :io  IK: l Y ' U i u l  to o c c u r i n the a f t e r n o o n  under e x t r e m e l y q u i e t c o n d i t i o n s ,  (the November 14, i 9 6 0  event i s one of such examples) but i t o c c u r s at a l e s s frequent rate.  The i m p u l s i v e type of P i 2 m i c r o p u l s a t i o n  126  u s u a l l y observed around midnight a l s o occurs Conditions  less frequently.  are g e n e r a l l y very q u i e t from dusk to a f t e r mid-  n i g h t although l e s s r e g u l a r p u l s a t i o n i n the Pc2 - 3 frequency range may s t i l l  be detected  Unfortunately,  i n a s s o c i a t i o n with bay.  good data obtained  during  stormy  c o n d i t i o n s are r a r e l y a v a i l a b l e at Great Whale R i v e r , as they are u s u a l l y recorded  o f f scale.  However,  Information  e x t r a c t e d from the a v a i l a b l e data I n d i c a t e s that  during  stormy c o n d i t i o n s , the d i u r n a l v a r i a t i o n observed under moderately d i s t u r b e d c o n d i t i o n s d e s c r i b e d above not only remains true but becomes more pronounced.  The frequency  of the p u l s a t i o n a c t i v i t y i s much h i g h e r i n g e n e r a l . night  The  time p u l s a t i o n events appear to be more v i o l e n t d u r i n g  stormy c o n d i t i o n s (e.g. the June 16, 1965 e v e n t ) . amplitude Pc5 may be observed c o n t i n u o u s l y c u l a r l y so i n the morning and i n the l a t e ,  Large  a l l day, p a r t i afternoon.  One example i s shown i n P i g . V.3f where Pc5 i s observed at both high and mid l a t i t u d e s t a t i o n s , a l l with Pc3 r i d e r s .  FIG. V.3a DIURNAL REGIONS ACTIVITIES AT THE HIGH  OF MICROPULSATION AND MID-LATITUDES  FIG. V. 3b  GREAT  WHALE  SEPT 2 0 1965  X  FIG. V. 3c  GREAT  FIG V.3b & V.3c  WHALE  DEC 19 1965  BAY ASSOCIATED Pc3  J U.T.  L  I  I  0 9 1 5  I  I  I  I  FIG V.3e January 21,1964  I  0°20  L A T I T U D E  »  DEPENDENCE  I  OF  P  C 3  ,U  J  1  L  FIGV.3f  APRIL 18,  1964  Pc5 WITH Pc.3 RIDERS  132  V.4  LATITUDE DEPENDENCE OF Fc3 FREQUENCY The c l a s s i f i c a t i o n scheme proposed i n Chapter I I I  p r o v i d e s a g e n e r a l g u i d e l i n e f o r r e s e a r c h on l a t i t u d e and l o c a l time dependence o f P c 3 f r e q u e n c y , f u r t h e r of which a r e t o be p r e s e n t e d i n t h i s s e c t i o n .  results Observations  made a t R a l s t o n a r e a g a i n chosen as a base f o r comparison w i t h o b s e r v a t i o n s made a t o t h e r s t a t i o n s . The m u l t i - b a n d s t r u c t u r e d P c 3 event observed a t R a l s t o n and d e s c r i b e d i n d e t a i l i n S e c t i o n I I I . 2 has been d i s p l a y e d a l o n g s i d e t h e dynamic spectrum o f t h e same event s i m u l t a n e o u s l y observed a t C o l l e g e , A l a s k a (Q - 64.7°). The d i s p l a y i s shown i n t h e lower p o r t i o n o f F i g . V.4a. S i m u l t a n e i t y o f o c c u r r e n c e and g e n e r a l appearance  of Pc3  observed at, t h e s e two s t a t i o n s i s most remarkably demonstrated  on t h e diagram.  T h i s i s p a r t i c u l a r l y so i n  the lower f r e q u e n c y bands where no l a t i t u d e o r l o c a l time dependence o f f r e q u e n c y i s observed i n t h e day regime.  The  n i g h t t i m e p u l s a t i o n a c t i v i t y observed at' around OB U.T. i s d e f i n i t e l y more v i o l e n t a t t h e h i g h e r l a t i t u d e . I t i s v e r y i m p o r t a n t t o note t h a t the m u l t i - b a n d s t r u c t u r e so apparent a t R a l s t o n from 1700 U.T. t o 210C U.T. ( i . e . around l o c a l noon) i s o n l y b a r e l y i n e x i s t e n c e a t College.  The 40 mHz band observed a t R a l s t o n becomes v e r y  weak i n t h e h i g h e r l a t i t u d e .  T h i s band becomes s i g n i f i c a n t  at C o l l e g e o n l y a f t e r 2300 U.T.  From 2300 U.T. t o 0100 U.T.  133  the f r e q u e n c y o f t h e band I s comparable  a t t h e two s t a t i o n s .  The same event r e c o r d e d on magnetograms o p e r a t i n g a t c h a r t speed o f 6 i n c h e s p e r hour has a l s o been observed a t Great Whale which i s l o c a t e d a t an even h i g h e r l a t i t u d e than C o l l e g e .  geomagnetic  T h i s has been compared w i t h magneto-  grams r e c o r d e d w i t h the same r e c o r d i n g speed a t R a l s t o n . P a r t o f t h e magnetogram ( f r o m 1400 U.T. t o m i d n i g h t i s i l l u s t r a t e d i n t h e upper p o r t i o n o f F i g . V.4a.  U.T.) Scaling  of these two magnetograms r e c o r d e d a t t h e two s t a t i o n s i n d i c a t e s t h a t t h e h i g h f r e q u e n c y component observed a t R a l s t o n i s c o n s t a n t l y o f h i g h e r f r e q u e n c y than t h a t observed at Great Whale.  The h i g h e s t f r e q u e n c y component observed  a t R a l s t o n i s a p p r o x i m a t e l y 46 mHz o c c u r r i n g around 1700 U.T., whereas t h e h i g h e s t f r e q u e n c y observed a t Great Whale i s o n l y about 25 mHz w i t h i n t h e same time i n t e r v a l .  The f r e q u e n c y o f  the p u l s a t i o n a c t i v i t y a t R a l s t o n d e c r e a s e s from 46 mHz a t 1700 U.T. t o 35 mHz a t 2100 U.T. w i t h m u l t i - p e r i o d i c i t y apparent throughout t h i s time i n t e r v a l .  The f r e q u e n c y o f  the c o r r e s p o n d i n g a c t i v i t y observed a t Great Whale i n the same i n t e r v a l i s o b v i o u s l y o f much l o w e r f r e q u e n c y and i t s f r e q u e n c y changes o n l y 4 mHz from 25 mHz a t 1700 U.T. t o 21 mHz a t 2100 U.T.  U n l i k e R a l s t o n , s c r u t i n y o f t h e same  event observed a t Great Whale shows no c l e a r e v i d e n c e o f m u l t i - p e r i o d i c i t y i n the P c 3 f r e q u e n c y range.  The d i u r n a l  v a r i a t i o n of amplitude of m i c r o p u l s a t i o n takes p l a c e at both R a l s t o n and Great Whale,  Note, f o r example, t h a t t h e  134  a m p l i t u d e o f t h e wave packet o c c u r r i n g around 1815 U.T. at Great Whale i s a p p r o x i m a t e l y 3.15 7 ( a t 25 mHz) whereas the c o r r e s p o n d i n g wave packet observed a t R a l s t o n i s o n l y 1.7 7 i n a m p l i t u d e ( a t 40 mHz).  Maximum i n t e n s i t y o c c u r s  around 1900 U.T. a t b o t h s t a t i o n s and d i m i n i s h e s from t h e n on t o reach i t s l o w e s t v a l u e a t a p p r o x i m a t e l y 2200 U.T. The b e a u t i f u l P c 3 event o f a p p r o x i m a t e l y 30 mHz i n f r e q u e n c y t h a t appears a f t e r 2300 U.T. a t R a l s t o n i s v e r y i n t e r e s t i n g because i t i s o f much g r e a t e r i n t e n s i t y (  1.6 7) than t h e c o r r e s p o n d i n g event observed a t  Great Whale ( - 0.5 7). T h i s may be p a r t l y due t o t h e l o c a l time dependence. Another example s i m i l a r t o t h e one d e s c r i b e d above i s shown i n F i g . V . 4 b . I n t h e lower p o r t i o n o f t h e diagram, sonagrams produced from d a t a r e c o r d e d a t C o l l e g e and R a l s t o n have been d i s p l a y e d f o r comparison. component  The h i g h e r f r e q u e n c y  (35 mHz) observed a t R a l s t o n i s a g a i n found t o  be much s t r o n g e r i n s i g n a l s t r e n g t h t h a n t h e c o r r e s p o n d i n g component observed a t C o l l e g e .  The o t h e r f r e q u e n c y components  are comparable i n f r e q u e n c y , time o f o c c u r r e n c e and i n s i g n a l s t r e n g t h between t h e two s t a t i o n s .  A s i m i l a r trend of  d i u r n a l and l a t i t u d e dependence of pc3 observed by s c a l i n g magnetograms i s a l s o e v i d e n t a t Great Whale and R a l s t o n . In F i g . V.4c, magnetograms from Great Whale (the upper magnetogram)  and from R a l s t o n have been shown s i d e by s i d e  f o r comparison.  T h i s p a r t i c u l a r event has a l r e a d y been  135  described of  i n detail  t h e same e v e n t  However, Pc3  as i t has been c l e a r l y  (1200  The  frequency,  Pc3 a c t i v i t y  Ralston)  Whale.  U.T.  1900  t o around  U.T.  But the rate  frequency  i s much g r e a t e r a t G r e a t  higher  of decrease  Ralston station.  observed  a t G r e a t Whale  at  i t s minimum.  Whale is  regular.  frequency  However,  quiet  1967  College  inverted observed  latitudes. 2o,  Whale  than  activity  often  be f o u n d  at Ralston.  which  t o what i s found  observed  usually  conditions  t o be  at Great  sec t o  i n the afternoon,  variation  (see Fig.V.4d). o f Pc3  at R a l s t o n under moderately t o  has a counterpart at the higher  I n F i g . V.4e, an e v e n t  and o b s e r v e d  has been  a m p l i t u d e and  P c 2 o f 10  to occur  U-type o f d i u r n a l  i s of  at the mid-  of smaller  very regular  and  a m p l i t u d e and  have no c o u n t e r p a r t i n t h e m i d l a t i t u d e s The  very  i n both  Pc3 a c t i v i t y  The p u l s a t i o n  20 s e c p e r i o d s may which  where  shown).  higher at the  Whale  This i s contrary  i n the afternoon i s usually  less  Great  (40 mHz), i s v e r y a c t i v e  latitude  event  (0600 L . T . a t  a f t e r n o o n t y p e o f Pc3 p u l s a t i o n ,  frequency  18  as the amplitude of  U.T.  at both  Ralston.  The  only i n the  i s slightly  1300  from  correlation  i n the October  The f r e q u e n c y a s w e l l decrease  spectrum  i n F i g . V.3c,  Close  Pc3 i s f o u n d  on t h e o t h e r hand,  mid-latitudes. the  t o 1830  U.T.  t h e dynamic  demonstrated  at Great  b e t w e e n h i g h and m i d - l a t i t u d e  where  i n F i g . III.3a f o r Ralston.  i s displayed  behaves d i f f e r e n t l y  morning  III.3  i n Section  taking  p l a c e on F e b r u a r y  s i m u l t a n e o u s l y a t b o t h R a l s t o n and  has been d i s p l a y e d  f o r comparison.  No  latitude  136  dependence o f P c 3 f r e q u e n c y has been o b s e r v e d between t h e two  stations.  The mean f r e q u e n c y o f Pc-3 e v e n t s I s f o u n d  t o be t h e same a t b o t h The at  1 2 0 0  stations.  wide band o f a c t i v i t y ( P i 2 )  U.T. and loOO U.T.  (i.e. 0 2 0 0  a t C o l l e g e ) was n o t o b s e r v e d to  l o c a l time dependence.  i n t i m e ahead o f C o l l e g e , it  i s already early Another  is  T h i s may be due  Because R a l s t o n i s t h r e e  i n the day regime.  interesting  f e a t u r e t o be n o t e d  close correspondence  at Ralston. of the frequency of the  q u i e t c o n d i t i o n s c o u l d n o t be f o u n d o f even h i g h e r l a t i t u d e  on F i g . V . 4 e  at College.  a c t i v i t y b e t w e e n R a l s t o n and C o l l e g e u n d e r  ahead o f R a l s t o n .  hours  i t may n o t o c c u r a t R a l s t o n w h e r e  t h e t r a c e o f P c 4 a c t i v i t y ( 1 0 milz) o b s e r v e d  The  is  L.T. and OoOO L.T.  at Ralston.  No d i s t i n c t P c 4 h a s b e e n o b s e r v e d  Pc3  invading college  moderately  a t G r e a t Whale  and i s two h o u r s  which  i n local  The two s o n a g r a m s o b t a i n e d f r o m  time  data  r e c o r d e d a t G r e a t Whale and R a l s t o n a r e shown i n F i g . V . 4 f c o v e r i n g two d a y s i n t i m e i n t e r v a l A latitude  ( F e b . 26 and 27,  d e p e n d e n c e o f mean f r e q u e n c y o f P c 3 i s f o u n d t o  be c o n s i d e r a b l e b e t w e e n t h e two s t a t i o n s . the  1967),  At Great  Whale,  s e p a r a t i o n b e t w e e n t h e P c 3 and P c 4 b a n d s i s n o t a t a l l  clear  (the e x i s t e n c e of which  latitudes).  An a v e r a g e  i s doubtful at the high  o v e r t h e two bands would  a l o w e r v a l u e o f t h e mean p u l s a t i o n f r e q u e n c y . mean f r e q u e n c y o b s e r v e d  result i n Thus t h e  a t G r e a t Whale i s much l o w e r  than  137  t h a t observed a t R a l s t o n .  Also, the amplitude of P c 3 at  the h i g h l a t i t u d e s t a t i o n appears t o be a maximum e a r l y i n t h e morning (OoOO L . T . ) , c o n t r a r y t o the noon maximum observed a t both R a l s t o n and C o l l e g e f o r t h i s type of d i u r n a l v a r i a t i o n of P c 3 frequency. The l o c a l time dependence as w e l l as t h e l a t i t u d e dependence have a profound e f f e c t on t h e P c 3 c u t - o f f .  The  P c 3 range of m i c r o p u l s a t i o n c u t s o f f a t around 1300 U.T. F e b r u a r y 26, 1967 a t Great Whale and n e a r l y t e r m i n a t e s a t m i d n i g h t U.T. a t R a l s t o n ( F i g . V . 4 f ) , w h i l e the same event l i n g e r s on u n t i l a f t e r 0400 U.T. on F e b r u a r y 27, 1967 a t College.  138  FIG.V.4a  Multi-Band Structured Pt 3  139  13  FEB  V  80 -60  FIG.V.4b  Multi-Band Structured Pc3  140  §.717  1.1*7  13  15  GW-/  OCT £9,67  \ • • V"'"\  \ ' ' V  ' \ ' " A C | C F (9,67 \  29 w  -  r l U . V.4C  ' OUT  *n  4  AA-  1o i3o7 v  '' \ " •  V  U.T.  LATITUDE DEPENDENCE OF NORMAL TYPE OF Pc3  -6*  1.45V at0.5Hz  GW  r  0.65 at0.5Hz  0.32 V at 0.5Hz  MG  2.72r at0.5Hz 2100  2105  FIG V.4d  September 19 1965 Pc3 AT TIE MID-LATITUDES  2110  142  College X  Ralston X  FIG.V.4e  FEBRUARY 26, 1967  SIMULTANEITY OF THE INVERTED U-TYPE OF Pc3 AT MID- AND HIGH-LATITUDES  14-3.  FIG V.4f  Latitude Dependence  of  Pc3  C O N J U G A C Y OF P c 3 AT H I G H AND M I D D L E L A T I T U D E S  V.5  Conjugate  studies  made i n t h e p r e s e n t Byrd,  Antarctica  weeks'  data  i s found  activity are on  research mainly  and G r e a t  however t h a t  conjugate  field  pair  During period  the  field  geomagnetic).  study  at Fights  and E i g h t s  extremely quiet Pc3's  (sometimes  conditions  (K  - 0 —>  Pc4) a r e o b s e r v e d  This type  of activity  and i s o b s e r v e d  s t a t i o n s a r e on t h e d a y l i g h t  side  f o r the very regular  i n the afternoon.  Only  shows v e r y  of the earth.  the nearly  are  t o be t a k e n i n t o c o n s i d e r a t i o n .  have been  a v a i l a b l e from Sights  But  good,  i f not better,  for  the mid-latitude  disturbed,  conjugacy  pairs.  becomes m o d e r a t e l y the conjugacy  when Three conjugacy  i n t h e morning  s i n u s o i d a l waves  Unfortunately,  under  1)  at both  mainly  waves, b o t h  and  condition  recorded  of s t a t i o n s i n the mid l a t i t u d e s .  peak t o peak conjugacy  observed  pulsation  are near  e x a m p l e s a r e shown i n F i g . V . 5 a w h e r e p e a k t o p e a k is  tvio  recorded a t McGill  to the signals McGill  Only  F) are a v a i l a b l e  0 « 355.3°  component  of stations  Canada.  i n most c a s e s under  component.  3yrd a n d G r e a t W h a l e . good  (total  on t h e X o r Y f i e l d  the total  at the pair  River,  (a) = 6 3 . 8 ° ,  Antarctica  s i m i l a r i n appearance  longer  Whale  i n one component  from Eights, It  of the continuous pulsation are  very quiet  no d a t a  conditions.  o f Pc3 i s t o be e x p e c t e d  I n f a c t , even  when t h e m a g n e t i c  disturbed, • but n o t v i o l e n t l y  o f ?c3 r e m a i n s  good  i n the mid-  latitudes.  themid-latitude Conjugacy  at  o f such  i s shown a t t h e b o t t o m o f  V.5a where p e a k t o p e a k c o n j u g a c y h a s b e e n  Fig. for  One e x a m p l e  the 3yrd-Great  Occasionally  pairs.  of t h e dawn "hale pair  peak  observed  and dusk  t y p e ?c2,3  i s apparent  t o peak correspondence  observed  activity  i noverall  however.  i s seen,  An e x a m p l e i s s h o w n on F i g . V.fjb f o r e a c h o f t h e s e t w o c a s e s  When t h e g e n e r a l l e v e l o f m a g n e t i c reasonably latitude  high  pair  (K = •'-!-), P c 3 a c t i v i t y o b s e r v e d a t t h e m i d -  d i s p l a y s more  than  at the high-latitude  event  shewn i n F i g . V . 5 c  Pc3 a c t i v i t i e s to  disturbance i s  observed  peak t o peak  pair.  correspondence  The S e p t e m b e r  i s one such i n the local  example. morning  16,  1965  I n general, are found  show c l o s e r c o n j u g a c y t h a n t h o s e o c c u r r i n g i n t h e  afternoon. When t h e m a g n e t i c  level  o f d i s t u r b a n c e becomes  very  high (Kp - 6 ) , Pc3 a c t i v i t i e s a r e no l o n g e r c o n j u g a t e a t the  G r e a t Whale-Byrd p a i r .  example.  T h e Pc.3 a c t i v i t y  F i g . V.5<3 s h o w s o n e s u c h i s c o n j u g a t e , and o c c a s i o n a l l y 0600 U.-T. o n J u n e  peak t o peak c o n j u g a t e , around = 1.  when  K  seen  that  I n the lower portion  of F i g . V.5d,  c o n j u g a c y becomes p o o r e r as K  15,  1965  i t i s  increases  further  £''  (0500 U.T. J u n e longer  (around  overall  oscillations  level  196.5),  When K  conjugate.  afternoon the  16,  I030  and f i n a l l y increases  U.T.),  substantially  the conjugacy  of a c t i v i t y ;  cannot  activities  necessarily  however, be  a r e no i n the  i s apparent i n  individual  correlated.  1 4 6  1.96  7  at 0 . 5 H2  GW  0.79 r at 0 . 5 Hs J  L  J  I  1520  l_  J  I  I  L  1525  December 14 1965  Kp = 1-  l.Q?. 7 a t 0 . 5 Ks  GW  0.25  7  at 0 . 5 Hz  '  '  '  1220  1_  J  I  L  J  '  I  1225  December 17 1965  Kp = 0+  1.52 7 at 0 . 5 Ks 2.31 7 at 0.5 H 3  GW  1804  -i  1  u  1  1810  1815  j  i_  June 24 1965 Kp<=1+  MG  r 1 0.32  7  a t 0 . 5 H' 0 . 0 4  y  a t 0 . 5 Hz  U. T.  1035  _1  r_  J  I  I  1040  September 19 1965  L  1043 Kp = 3-  FIG V5a CONJUGACY OF Pc3  0810 September 20 1965  0815  U.T.  FIG V.5b CONJUGACY OF DAWN AND DUSK TYPE Pc2,3  GW-Y 1.44  r  at O J H Z  Vlato-sHr  0.86 i" atasH:  0.24 TT  at 0.5 Hz  0.24 f  at o.3 Hz  0.04 7^" ato^sHx  L  J  I  L  J  1550  FIG  riva  V  I  I  L  U.T.  1555  *r  v.oc  Qpnt  oept  I R T O ,  f a c e  Iyoo  CONJUGACY OF HIGH AND M I D  P 3  AT C LATITUDES  150  V.6  .DISCUSSIONS I n Chapter I I I , t h e e x i s t e n c e o f e i g e n  oscillations'  of m o d i f i e d A l f v e n mode o u t s i d e the plasmapause i n t h e plasmatrough has been p o s t u l a t e d , i n a d d i t i o n t o t h e e i g e n o s c i l l a t i o n a l r e a d y w i d e l y b e l i e v e d t o e x i s t i n s i d e the plasmasphere.  T h i s model has been used t o e x p l a i n t h e  e x i s t e n c e of d i f f e r e n t t y p e s o f d i u r n a l v a r i a t i o n of P c 3 frequency  e x p e r i m e n t a l l y observed  at Ralston.  The same  model has been used a l s o t o i n t e r p r e t r e s u l t s on K P  dependence o f P c 3 f r e q u e n c y been found t h a t e x p e r i m e n t a l  s t u d i e d i n Chapter IV.  I t has  r e s u l t s o b t a i n e d so f a r agree  w i t h t h e o r e t i c a l p r e d i c t i o n s i m p l i e d by t h e proposed model. I n t h i s s e c t i o n , the same model w i l l a g a i n be employed t o I n t e r p r e t r e s u l t s r e p o r t e d i n the e a r l i e r s e c t i o n s . The  fjj_ band o f P c 3 p u l s a t i o n i d e n t i f i e d i n S e c t i o n  I I I . 2 and i n Chapter IV has been c o n s i d e r e d t o be a h i g h l a t i t u d e phenomenon o r i g i n a t i n g i n the  plasmatrough,  whereas t h e f _ band of P c 3 i s c o n s i d e r e d t o o r i g i n a t e i n 3  the plasmasphere bounded by the plasmapause. the m u l t i - b a n d  Occurrence o f  s t r u c t u r e d P c 3 a t R a l s t o n has been thought o f  as a boundary e f f e c t which t a k e s p l a c e when R a l s t o n I s s i t u a t e d c l o s e t o t h e plasmapause.  I f t h i s i s indeed t h e  case, s t a t i o n s o f h i g h e r l a t i t u d e than R a l s t o n observe P c 3 t h a t has f r e q u e n c y observed  should  comparable t o the f ^ band  s i m u l t a n e o u s l y a t R a l s t o n under moderately  disturbed  151  conditions. observed  On the o t h e r hand, the f r e q u e n c y o f Pc3  events  at s t a t i o n s o f lower l a t i t u d e than R a l s t o n would  be dominated by the f ^ band.  Close examination  of  magnetograms s i m u l t a n e o u s l y o b t a i n e d from R a l s t o n , C o l l e g e and Great Whale have i n d i c a t e d t h a t Pc3 i n the h i g h e r l a t i t u d e s i n d e e d behaves as p r e d i c t e d by the proposed model. The  two examples g i v e n i n F i g . V.4a  and F i g . V.4b  are o n l y  two of many examples t h a t c o u l d show the f ^ band t o be  very  weak i n the h i g h e r l a t i t u d e s b e f o r e noon. The l o w e r f r e q u e n c y component ( <^> 25 Pc3 has been observed  t o 30 mHz)  of  s i m u l t a n e o u s l y a t both h i g h and  mid  l a t i t u d e s t a t i o n s w i t h comparable i n t e n s i t y .  This  obser-  v a t i o n a l f a c t c o u l d not be i n t e r p r e t e d c o r r e c t l y w i t h o u t p r i o r knowledge of the s i m u l t a n e o u s  behaviour of  p a r t i c u l a r f r e q u e n c y band at t h e l o w e r The  event observed  this  latitudes.  s i m u l t a n e o u s l y at R a l s t o n  and  C o l l e g e i n the a f t e r n o o n i s o f p a r t i c u l a r i n t e r e s t . may  be taken as f u r t h e r e v i d e n c e o f the east-west  This  asymmetry  of the plasmapause c o n f i g u r a t i o n . Under m o d e r a t e l y c o n d i t i o n s , as i n the February  11, 1967  a  disturbed  event shown ( F i g . V . 4 a ) ,  R a l s t o n u s u a l l y i s v e r y c l o s e t o the plasmapause.  College,  b e i n g a t a h i g h e r geomagnetic l a t i t u d e than R a l s t o n , i s u s u a l l y w e l l o u t s i d e the plasmapause.  This i s p a r t i c u l a r l y  so i n the morning when the g e o c e n t r i c d i s t a n c e o f the plasmapause i s at i t s minimum ( C a r p e n t e r , 1966).  As  the  g e o c e n t r i c d i s t a n c e o f the plasmapause i n c r e a s e s t o i t s  152  maximum l a t e r i n the a f t e r n o o n , both R a l s t o n and may  be found i n s i d e  College  the plasmapause, i n which case the f ^  band of P c 3 would be observed at R a l s t o n as w e l l as at C o l l e g e i n s t e a d of the o t h e r P c 3 band t h a t was e a r l i e r i n the day. f o r the o c c u r r e n c e  T h i s i s the phenomenon r e s p o n s i b l e of the event s i m u l t a n e o u s l y  at R a l s t o n and C o l l e g e around m i d n i g h t 1967  shown i n F i g . V.4a.  vaguely  observed  The  U.T.  observed 11,  February  same event was  observed o n l y  at Great Whale because the l a t i t u d e i s so h i g h  t h a t no boundary c r o s s i n g took p l a c e . U n f o r t u n a t e l y , no d a t a s i m u l t a n e o u s l y lower l a t i t u d e s t a t i o n have been a v a i l a b l e  recorded  at a  f o r comparison.  However, v a r i o u s workers have r e p o r t e d r e s u l t s of t h e i r o b s e r v a t i o n s , b o t h i n the low and i n the m i d - l a t i t u d e stations.  These r e s u l t s have been t a b u l a t e d i n Table V . l  to show the mean f r e q u e n c y authors  at d i f f e r e n t I t may  of Pc3 observed'by d i f f e r e n t  latitudes.  be seen from Table V . l t h a t the mean  of Pc3 observed by most workers at geomagnetic lower than 60° different  i s around 30 to 45 mHz.  frequency  latitudes  A l l o w i n g f o r the  s c a l i n g methods used by d i f f e r e n t a u t h o r s ,  a l s o b e a r i n g i n mind the l i m i t a t i o n of the  and  statistical  methods employed, the r e s u l t i s i n v e r y good agreement w i t h the f ^ band of P c 3 t h a t has been observed at R a l s t o n .  This  i s c o n s i s t e n t w i t h our s p e c u l a t i o n t h a t the f ^ band of  Pc3  i s a mid-  and  l o w e r - l a t i t u d e phenomenon o r i g i n a t i n g  the I n s i d e of the plasmasphere.  from  153  I n C h a p t e r I I I , the morning type of P c 3 observed at R a l s t o n on October 18, 1967 under m o d e r a t e l y d i s t u r b e d c o n d i t i o n s has been s p e c u l a t e d t o be a h i g h - l a t i t u d e phenomenon t a k i n g p l a c e when R a l s t o n i s i n the p l a s m a t r o u g h , whereas the a f t e r n o o n type of P c 3 o c c u r r i n g on the same day i s considered  t o o r i g i n a t e i n s i d e the plasmasphere and i s  observed o n l y a f t e r boundary c r o s s i n g t o o k p l a c e e a r l y i n the a f t e r n o o n .  This i s consistent with r e s u l t s  i n S e c t i o n V.4 where the same event r e c o r d e d  reported  simultaneously  on c h a r t s at R a l s t o n and Great Whale has been compared. I t was  found t h a t c l o s e c o r r e l a t i o n between P c 3 observed  at R a l s t o n and t h a t observed at Great Whale e x i s t s o n l y i n the morning when the i n t e n s i t y of the P c 3 a c t i v i t y i s much g r e a t e r at Great Whale t h a n at R a l s t o n .  This i s a  c l e a r e v i d e n c e t h a t the morning type of P c 3 observed at R a l s t o n i s a h i g h - l a t i t u d e phenomenon. The  a f t e r n o o n type of P c 3 observed at R a l s t o n i n  the a f t e r n o o n , however, has no c o u n t e r p a r t latitudes.  i n the  high  T h i s a g a i n i s c o n s i s t e n t w i t h the s p e c u l a t i o n  t h a t the a f t e r n o o n type of P c 3 observed at R a l s t o n may  have  o r i g i n a t e d from the i n s i d e of the plasmasphere. S i n c e under q u i e t c o n d i t i o n s , the plasmapause expands r a d i a l l y , i t i s not s u r p r i s i n g t o f i n d the c l o s e c o r r e l a t i o n between the i n v e r t e d U-type of d i u r n a l v a r i a t i o n of frequency  observed at R a l s t o n and t h a t observed at C o l l e g e ,  154  as both of them are e x p e c t e d t o be found i n s i d e t h e plasmapause.  When t h e c o n d i t i o n s become e x t r e m e l y q u i e t ,  then the P c 3 a t Great Whale t o o would have t h e same f r e q u e n c y and t h e same d i u r n a l b e h a v i o u r as a t the o t h e r s t a t i o n s i n t h e lower l a t i t u d e s . • The l o c a l time dependence o f t h e P c 3 c u t - o f f may a l s o be e x p l a i n e d a f t e r the asymmetry o f t h e plasmapause c o n f i g u r a t i o n has been t a k e n i n t o account.  The boundary  c r o s s i n g s h o u l d take p l a c e t h r e e hours e a r l i e r a t R a l s t o n than a t C o l l e g e .  TABLE LATITUDE  DEPENDENCE BY  Observer  Nagata and Fukunishi  1968  Hirasawa and N a g a t a 1966 Kato and Saito 1959 ( D u r i n g SSC) 1961  Duncan Campbell Maple  1959  1959  Berthod, Harris and Hope i 9 6 0  OTHER  Data  V. 1 OF  Pc3  REPORTED  OBSERVERS  Observatory  Geomag. P e r i o d Lat. (Sec)  F r e q u e :n c y (mHz  Chart and T a p e s  Kakioka  26°  28  35  Chart and T a p e s  Kakioka  26°  28  35  Chart  Onagawa  28°  20  50  Chart  Townsville  29°  19  52  Chart  Borrego  39°  22  45  Chart  Tucson  40°  20  50  Chart  Arizona  41°  35  29  Duncan  1961  Chart and T a p e s  Adelaide  45°  23  U  Duncan  1961  Chart and T a p e s  Hobart  52°  27  37  0  S c h o l t e and V e l d k a m p 1955  Chart  Witteveen  54°  45  22  S t u a r t and U s h e r i960  Chart  Hartland  55°  40  25  S t u a r t and U s h e r 1966  Chart  Eskdalemuir  59°  25  40  Chart  Eskdalemuir  50°  25  4 0  Chart  Lerwich  63°  30  33  Holmberg  1953  S t u a r t and U s h e r i960  156  CHAPTER GENERAL  VI. 1  VI  STUDIES  OF  Pc4  INTRODUCTION A l t h o u g h t h e e x a c t m o r p h o l o g i c a l p r o p e r t i e s of P c 4  i s n o t y e t understood  and t h e r e remains c o n t r o v e r s y t o be  r e s o l v e d i n b o t h e x p e r i m e n t a l o b s e r v a t i o n s and t h e t h e o r e t i c a l c o n s i d e r a t i o n ' s r e p o r t e d by v a r i o u s r e s e a r c h e r s s i n c e the IGY, many a u t h o r s b e l i e v e t h a t t h e P c 3 and P c 4 t y p e s o f c o n t i n u o u s p u l s a t i o n s are c l o s e l y c o r r e l a t e d . I n f a c t , i t has been common p r a c t i c e by some a u t h o r s t o use P c 3 , 4, o r s i m p l y Pc, as a u n i f y i n g n o t a t i o n t o denote b o t h the P c 3 and Pc4  t y p e s o f m i c r o p u l s a t i o n s ( V o e l k e r , 1967; S i e b e r t , 1 9 6 4 ) .  On t h e o t h e r hand, S a i t o (1966) regarded P c 4 as e s s e n t i a l l y an e x t e n s i o n o f P c 5 because P c 4 has so many m o r p h o l o g i c a l c h a r a c t e r i s t i c s similar to Pc5.  The p r e c i s e f r e q u e n c y  boundary, i f t h e r e i s any, o f P c 4 c a n be l o c a t e d o n l y a f t e r the e x a c t n a t u r e o f i t s g e n e r a t i n g and p r o p a g a t i n g mechanism becomes u n d e r s t o o d .  F o r t h i s purpose, t h e m o r p h o l o g i c a l  p r o p e r t i e s o f P c 4 must f i r s t be s t u d i e d i n d e t a i l . The d i u r n a l v a r i a t i o n o f P c 4 f r e q u e n c y has been observed frequency  by Katp and S a i t o t o behave as an i n v e r t e d U-type i n (U-type  i n p e r i o d ) w i t h minimum f r e q u e n c y o c c u r r i n g  j u s t b e f o r e t h e noon hour (Kato and S a i t o , 1959, 1962; S a i t o , 1962,  1964a).  T h i s i s c o n t r a r y t o the l a t e r r e p o r t of  Hirasawa and Nagata (1966) and Nagata and F u k u n i s h i (1968) who  157  observed  t h a t t h e P c 4 (15 mHz) band o f p u l s a t i o n appears  throughout almost a day, b e i n g most a c t i v e around 0900.L.T. w i t h minimum a t about 19 L.T. U s i n g d a t a o b t a i n e d d u r i n g t h e q u i e t sun p e r i o d , 1964 and 1965, Hirasawa and Nagata (1966) have shown t h a t t h e frequency  o f t h e 15 mHz band i n c r e a s e s w i t h i n c r e a s i n g  geomagnetic a c t i v i t y r e p r e s e n t e d by 51 Kp.  Nagata and  F u k u n i s h i (1968) even d e r i v e d an e m p i r i c a l r e l a t i o n  expres-  s i n g t h e l i n e a r r e l a t i o n between t h e maximum c e n t r a l of P c 4 , i . e . t h e mean f r e q u e n c y of maximum d a i l y f r e q u e n c y  frequency  o f P c 4 s c a l e d a t t h e time  occurrence,  and t h e average v a l u e  of Kp (Kp) o r t h e sum o f Kp ( % K p ) . These f i n d i n g s have p r o f o u n d l y a f f e c t e d t h e t h e o r e t i c a l model one may use t o interpret  experimental observations reported i n the previous  chapters. The  l a t i t u d i n a l dependence o f P c 4 amplitude  s t u d i e d by a few r e s e a r c h e r s . t h a t t h e maximum amplitude  has been  Kato and S a i t o (1962) r e p o r t e d  o f P c 4 seems t o be i n t h e a u r o r a l  l a t i t u d e and t h e r e seems t o be a secondary maximum e x i s t i n g i n t h e s u b - a u r o r a l zone ((j) ^ collected  50°).  E a r l i e r , Vledkamp ( i 9 6 0 )  d a t a from a wider d i s t r i b u t i o n of s t a t i o n s t h a n  t h a t used by Kato and S a i t o and found t h a t t h e r e i s a prominent maximum i n t h e s p a t i a l d i s t r i b u t i o n of P c 4 amplitude  near t h e s u b - a u r o r a l zones.  These o b s e r v a t i o n s are i n agreement w i t h those of Obayashi and Jacobs . (1958) who, u s i n g about 80 days o f r e c o r d s  15  in  there  i s a concentration  sub-auroral In based in  194-9  sunspot-minimum y e a r s from  on  c h a p t e r , we  a detailed  shall  study of the  frequency range.  form  of  tape  records are  those from  from  G r e a t Whale  River.  better other  rapid-run Esterline  quality  and  stations.  component  Only  component P  Pc4  from  report few  Angus c h a r t s . Ralston  the  as  a basis  The  available  to a lesser  extent of  of comparison  with  data  field  into As  the  i s the Y  f o r the h i g h  some r e s u l t s .  suggest  the  range  They  i n a m p l i t u d e and  This  agrees  from  the B y r d - G r e a t Whale  and  t o make  of  and  two  a of  latitudes,  (1965) h a v e  oscillations  in  appear s i m u l t a n e o u s l y Great Whale  o b s e r v a t i o n s o f more pair.  a period  Wright  that  period  of Byrd  field  conjugate behaviour  yielded  stations  over  T h i s e n a b l e s us  Jacobs  our  available  r e c o r d e d i n one  o b s e r v a t i o n made b y  with  and  from Eights  1965.  investigation  the conjugate  data  results  r e c o r d s are u s u a l l y  earlier  at  preliminary  limited  the R a l s t o n  i n the m i d - l a t i t u d e s .  Pc4  near  r e c o r d s are m a i n l y i n the  magnetograms  available  weeks i n September, preliminary  of p u l s a t i o n  that  f o r comparison.  rapid-run are  The  Ralston  are used  available  The  range  observed  zone.  this  t h e Pc4  o f Pc4  t o 1953,  River.  recent data  also  1 5 9  VI.2  DIURNAL VARIATION OF P c 4 AT THE MID-LATITUDE RALSTON STATION W i t h i n t h e f r e q u e n c y boundary  the  IAGA r e s o l u t i o n 1 9 6 4 ,  o f P c 4 d e f i n e d by  t h e r e are two d i f f e r e n t t y p e s o f  p u l s a t i o n a c t i v i t i e s t h a t may o f t e n be i d e n t i f i e d a t R a l s t o n . Roth t y p e s are observed m a i n l y i n the d a y t i m e . The f i r s t  type o f p u l s a t i o n a c t i v i t y observed a t  R a l s t o n under m o d e r a t e l y d i s t u r b e d c o n d i t i o n s (Kp = 3 - 4) is called  'Giant p u l s a t i o n  1  o r s i m p l y Pg i n t h i s  thesis,  a f t e r S u c k s d o r f f (1939) who f i r s t d i s c o v e r e d t h i s type o f phenomenon i n an a u r o r a l r e g i o n .  The term 'Pg' i s used  p r e s e n t l y i n a broader sense, however.  As f a r as t h e  f r e q u e n c y i s concerned, Pg i s P c 4 , b u t a Pg i s known t o be a v e r y l o c a l phenomenon. The f o c u s o f the p r e s e n t r e s e a r c h i s m a i n l y on t h e u s u a l type o f P c 4 t h a t o c c u r s under m o d e r a t e l y q u i e t conditions (IC.^ l->2).  T h i s type o f P c 4 may be observed  s i m u l t a n e o u s l y over a wide a r e a . The d i u r n a l v a r i a t i o n o f P c 4 observed a t R a l s t o n appears t o have a maximum i n f r e q u e n c y around 0600 L.T. and a minimum around noon o r e a r l y i n t h e a f t e r n o o n . at  Pc4 occurs  a l e s s f r e q u e n t r a t e i n t h e a f t e r n o o n t h a n i n t h e morning,  and the a f t e r n o o n P c 4 , when o b s e r v e d , i s u s u a l l y much l o w e r i n s i g n a l s t r e n g t h t h a n t h a t i n t h e morning.  There are  o c c a s i o n s , however, when t h e s i g n a l s t r e n g t h of P c 4 has been found t o be g r e a t e r i n t h e e a r l y a f t e r n o o n .  Events that  l6o  occur i n the a f t e r n o o n w i t h g r e a t i n t e n s i t y at R a l s t o n o n l y when t h e va.lue of the  are observed  index i s  r e l a t i v e l y high. I n P i g . V I . 2 a , an example i s shown where P c 4 had been a c t i v e a t R a l s t o n throughout the day, p a r t i c u l a r l y morning.  The maximum-frequency of P c 4  so i n the  20 mHz) o c c u r r e d  j u s t around 0600 L.T. t o r e a c h i t s l o w e s t v a l u e o f a p p r o x i m a t e l y 5 mHz particular  a t 1500 L.T.  The maximum a m p l i t u d e of t h i s  P c 4 event i s found t o o c c u r around 1000 L.T.  which  i s t h e time when the f ^ band of P c 3 becomes s i g n i f i c a n t . The correspondence between the o c c u r r e n c e o f P c 4 and the  o c c u r r e n c e o f the f  0  band of P c 3 a t R a l s t o n has been  3  found t o be e x t r e m e l y good.  One example of such i s  i l l u s t r a t e d i n P i g . VI.2b where the d i u r n a l v a r i a t i o n of Pc4 c o r r e s p o n d s c l o s e l y band of P c 3 . the  t o the d i u r n a l p a t t e r n of the f ^  The maximum f r e q u e n c i e s o f b o t h the P c 4 and  f ^ bands are found t o o c c u r around 0800 L.T. i n the  morning whereas the minimum f r e q u e n c i e s are observed l o c a l noon.  around  B o t h Pc4 and the f _ band of P c 3 were observed  to be i n b u n d l e s , each bundle r e p r e s e n t i n g a packet of waves.  F u r t h e r , the c o r r e s p o n d i n g p a c k e t s of waves of the  two d i f f e r e n t  bands appear t o be s t r i k i n g l y s i m i l a r .  Such  correspondence c o n t i n u e s , a l t h o u g h l e s s e a s i l y r e c o g n i z e d , even a f t e r  1400 L.T. when t h e f ^ band r a t h e r t h a n the f ^  band o f P c 3 dominates greater  intensity).  ( i n the sense t h a t i t i s o f much  1 6 1  There is  observed  are early  under moderately event Pc4  cases  where  i n the  a f t e r n o o n , but  disturbed conditions.  shown i n F i g . V I . 2 c  pulsation  around  1300  signal  L.T.  a relatively  of  i s one  10  mHz  soon a f t e r  such  s t r o n g Pc4  this The  occurs  only  November  13  example where a  In frequency  the  signal  f ^ band  i s  o f Pc3  strong  observed becomes  noticeable. Preliminary the  X  and  but  when t h e  high,  than  general level differ,  the X  This the in one  9*  1967  both  event  example c l e a r l y  the  finds  afternoon.  are comparable  of magnetic  amplitudes i n most  of  cases,  disturbances i s  Y component u s u a l l y  amplitude  difficulty  t h e X and  being  Y components of  have been d i s p l a y e d f o r  demonstrates  Y c o m p o n e n t o f Pc4 fact,  the  that the  much  component.  In F i g . VI.2d, February  Indicate  Y c o m p o n e n t s o f Pc4  t h e y may  larger  results  that the  i s much g r e a t e r t h a n of  the  in identifying  it,  comparison.  amplitude i t s X  X component i s so  the  of  component;  small that  particularly  i n the  162  FIG Vl.2a  February 24,1967  DIURNAL VARIATION OF Pc4  163  FIG Vl.2b RALSTON X NOV 9,67 SIMULTANEOUS OCCURRENCE OF P c 3 AND Pc4  164  FIG VI. 2c  RALSTON X  NOV 13,67  Pc4 IN THE AFTERNOON  FIG VI. 2d  COMPARISON OF THE X & Y FIELD COMPONENTS  166  VI.3  LATITUDE DEPENDENCE OF The  s o - c a l l e d 'Giant P u l s a t i o n ' (Pg) d e s c r i b e d  v a r i o u s a u t h o r s and reviewed observed  Pc4 by  by Kato (1964) has a l s o been  at R a l s t o n under m o d e r a t e l y d i s t u r b e d c o n d i t o n s .  Pg i s known t o be a l o c a l phenomenon which o c c u r s at h i g h l a t i t u d e s or i n the a u r o r a l zone. event of a p p r o x i m a t e l y  100  F i g . VI.3a shows a Pg  sec p e r i o d observed  and not at the o t h e r s t a t i o n s .  The  d u r i n g most of the day of August 17,  at M c G i l l  Pg a c t i v i t y took 1967  place  but o n l y a s m a l l  p o r t i o n of the p a r t i c u l a r event i s shown on the diagram for i l l u s t r a t i v e  purpose.  As f o r the u s u a l type of Pc4 t h a t o c c u r s under m o d e r a t e l y q u i e t magnetic c o n d i t o n s , i t has been w i d e l y r e c o g n i z e d t h a t t h i s type of Pc4 may t a n e o u s l y over a wide a r e a .  be observed  Indeed,  simul-  simultaneous  o b s e r v a t i o n s made at Great Whale, R a l s t o n and M c G i l l not o n l y i n d i c a t e t h i s t r e n d , but f u r t h e r , the Pc4 are found to be of the same One  observations  frequency.  t y p i c a l Pc4 event s i m u l t a n e o u s l y observed  at  Great Whale, 3 y r d , R a l s t o n , M c G i l l and E i g h t s i s shown i n F i g , VI.3b f o r comparison. observed  The  frequency  t o be the same at a l l s t a t i o n s .  of Pc4 The  was  amplitude,  however, i s s l i g h t l y g r e a t e r at R a l s t o n and M c G i l l ,  but  not to a s i g n i f i c a n t e x t e n t . The  conjugacy of Pc4 f o r both the B y r d - G r e a t Whale  167  p a i r I n t h e h i g h l a t i t u d e r e g i o n and t h e E i g h t s - M c G i l l in  pair  t h e m i d - l a t i t u d e s h a s b e e n f o u n d t o be e x t r e m e l y g o o d .  E v e n peak, t o p e a k c o r r e s p o n d e n c e h a s b e e n o b s e r v e d corresponding p a i r of It  between  stations.  i s r a t h e r u n f o r t u n a t e t h a t o n l y a v e r y few o f  the slow speed magnetic are of s u f f i c i e n t l y  tape d a t a recorded a t Great  low n o i s e to s i g n a l r a t i o .  Whale  T h i s does  n o t a l l o w us t o make a d e t a i l e d c o m p a r i s o n o f P c 4 o b s e r v e d a t t h e h i g h and t h e m i d - l a t i t u d e s t a t i o n s .  Preliminary  o b s e r v a t i o n s u s i n g the a v a i l a b l e d a t a , however, yielded  some i n t e r e s t i n g i n f o r m a t i o n .  have  Sonagrams  produced  f r o m s l o w s p e e d t a p e d a t a r e c o r d e d a t G r e a t Whale h a v e no d i s t i n c t  s e p a r a t i o n b e t w e e n t h e Pc3  and t h e Pc4  shown  bands,  c o n t r a r y t o what i s u s u a l l y o b s e r v e d a t t h e l o w e r  latitudes.  Often at Ralston,  when  and l e s s o f t e n ,  at College,  o b s e r v e d h a s b e e n f o u n d t o be a d i s t i n c t f r o m t h e Pc3. magnetic  may  of  f o r example, i n the event  storm.  The F e b r u a r y 24, 1967 clearly  band s e p a r a t e d  No s e p a r a t i o n i s o b s e r v e d when t h e l e v e l  disturbance i s high,  of a magnetic  Pc4  illustrates  e v e n t shown i n F i g . V I . 3 c  t h e phenomenon d e s c r i b e d a b o v e .  s e e on t h e d i a g r a m  t h a t no s e p a r a t i o n b e t w e e n t h e P c 4  and t h e Pc3 b a n d s h a s t a k e n p l a c e a t G r e a t Whale  contrary  t o t h e c l e a r two-band s t r u c t u r e o b s e r v e d a t R a l s t o n . F e b r u a r y 23, 1967  One  The  event, which o c c u r r e d under moderately  disturbed conditions,  d i d n o t show c l e a r band s t r u c t u r e a t  168  b o t h G r e a t w h a l e and R a l s t o n ,  but t h e r e I s a l o w - f r e q u e n c y  c u t - o f f a t a p p r o x i m a t e l y 10 mHz n o t a t G r e a t Whale.  observed at R a l s t o n ,  and  FIG  Pg ACTIVITY AT McGILL  M  170  11.42 r  GW-Y  I AT0.5HZ  BY-Y BY-X  ,2.72r 'AT0.5HZ  RA-Y  0.05 r AT0.5HZ  , 0.303 r  MG-Y-  'AT0.5HZ  MG-X  ,0.303 r  'AT0.5HZ  , 0.042 r IAT0.5HZ  EI-F J  22 SEPT65  i  i_  1140  1145  1150 U.T  FIG Vl.3b CONJUGACY & LATITUDE DEPEDENCE OF Pc4  171  80-  RALSTON X i i 1 1 i i I 1 1  U.T.,  0  23,67  FIG VI.3C  11 i I 11 i 11 I 11 i I  1 1 1 1 1 11 I I I ' I '  24,67  LATITUDE DEPENDENCE OF P e s  172  VI.4  DISCUSSION The  near  t h e s u b - a u r o r a l zone o b s e r v e d  (Obayashi 1962)  c o n c e n t r a t i o n o f t h e Pc4 range  and J a c o b s ,  has suggested  1958;  of p u l s a t i o n  by v a r i o u s a u t h o r s  V e l d k a m p , i960; K a t o  t h a t P c 4 may o r i g i n a t e  and S a i t o ,  at t h e plasmapause.  Such a s p e c u l a t i o n has been r e i n f o r c e d by t h e o b s e r v a t i o n made r e c e n t l y b y a r e s e a r c h g r o u p r e p o r t i n g f r o m ( H i r a s a w a and N a g a t a ,  1966;  Japan  N a g a t a and F u k u n i s h i ,  t h a t t h e d a i l y v a r i a t i o n c u r v e o f t h e 15 mHz b a n d (Pc4) on m o d e r a t e l y  1968) frequency  d i s t u r b e d d a y s (11 ^ Z K ^ ^ . 20) i s i n  good a g r e e m e n t w i t h a d a i l y v a r i a t i o n c u r v e o f t h e e i g e n f r e q u e n c y o f a s t a n d i n g A l f v e n wave a l o n g t h e f i e l d on t h e p l a s m a p a u s e , t h e o r e t i c a l l y d e r i v e d f r o m model o f t h e plasmapause  ( W i l s o n , 1963).  Carpenter's  A s i m i l a r trend of  d i u r n a l and l a t i t u d e b e h a v i o u r h a s b e e n o b s e r v e d l a t i t u d e Canadian  lines  a t the mid-  stations reported i n t h i s chapter.  a s t h e P c 4 band i s c o n c e r n e d ,  Insofar  therefore, the standing A l f v e n  wave on t h e p l a s m a p a u s e may be c o n s i d e r e d a s t h e most probable  resonator. . I f t h i s i s indeed the case,  frequency of a hydromagnetic the dimension  of the magnetic  since the eigen  o s c i l l a t i o n depends h e a v i l y on r e s o n a t o r , and t h e d i m e n s i o n s  o f t h e p l a s m a p a u s e and o f t h e p l a s m a s p h e r e related,  are c l o s e l y  i t w o u l d n o t be t o o s u r p r i s i n g t o f i n d  correspondence  between the o c c u r r e n c e  b e h a v i o u r o f P c 4 and t h a t o f t h e f  Q  the close  as w e l l as t h e d i u r n a l  band o f P c 3 o b s e r v e d a t  1 7 3  Ralston.  The  s i m i l a r i t y between the K  dependence of the  f ^ band of P c 3 and t h a t of P c 4 has a l r e a d y been d e s c r i b e d i n d e t a i l i n the l a s t c h a p t e r . One  example ( F i g . V I . 3 b )  has been g i v e n where the  Pc4 a c t i v i t y observed at b o t h mid- and s t a t i o n s are comparable  high-latitude  i n a m p l i t u d e as w e l l as i n p e r i o d .  T h i s type of 'Pc4' c o u l d not be i n t e r p r e t e d s i m p l y as a r e s u l t of a hydromagnetic plasmapause.  o s c i l l a t i o n o r i g i n a t i n g at the  R a t h e r , t h i s may  be t a k e n as e v i d e n c e t h a t  the e i g e n f r e q u e n c y of the p o l o i d a l o s c i l l a t i o n d e s c r i b e d i n the p r e v i o u s c h a p t e r s may  sometimes be found t o be v e r y  low, so low t h a t i t has passed the lower f r e q u e n c y boundary of P c 3 d e f i n e d by the B e r k e l e y r e s o l u t i o n .  Such an u l t r a -  low f r e q u e n c y P c 3 i s observed o n l y under v e r y q u i e t conditions.  magnetic  174  CHAPTER POSTCRIPT:  DISCUSSION  VII AND  FUTURE  EXPERIMENTS  The d i f f e r e n t forms of d i u r n a l v a r i a t i o n o f the ? c 3 f r e q u e n c y observed at R a l s t o n i n the year 1967 have been studied i n d e t a i l .  I t has been found and r e p o r t e d i n  Chapter I I I t h a t the m a j o r i t y o f them may be c l a s s i f i e d i n t o f o u r o r a c o m b i n a t i o n of f o u r b a s i c t y p e s .  In order  t o e x p l a i n the o c c u r r e n c e of d i f f e r e n t b a s i c t y p e s of d i u r n a l v a r i a t i o n of P c 3 , the e x i s t e n c e o f an e i g e n o s c i l l a t i o n of the m o d i f i e d A l f v e n mode I n the plasmatrough was proposed i n a d d i t i o n t o the e i g e n o s c i l l a t i o n the plasmasphere  inside  already widely believed to e x i s t .  U s i n g the proposed c l a s s i f i c a t i o n scheme as a g u i d e l i n e f o r f u r t h e r r e s e a r c h i n Chapter IV, the dependence of the f o u r b a s i c t y p e s of d i u r n a l v a r i a t i o n on the has been i n v e s t i g a t e d .  index  The e x p e r i m e n t a l r e s u l t t h u s o b t a i n e d  f u r t h e r r e i n f o r c e s the i d e a t h a t e i g e n o s c i l l a t i o n indeed e x i s t i n the plasmatrough.  may  I n f a c t , the r e s e a r c h r e -  p o r t e d i n Chapter IV e n a b l e s one t o i d e n t i f y the f r e q u e n c y component of P c 3 observed a t R a l s t o n as h a v i n g o r i g i n a t e d i n the plasmatrough. A c o m p a r a t i v e study o f s i m u l t a n e o u s o b s e r v a t i o n s made at b o t h h i g h and m i d - l a t i t u d e s t a t i o n s p r o v i d e s f u r t h e r support f o r the proposed model I n t h a t the f r e q u e n c y component b e l i e v e d t o o r i g i n a t e i n the plasmatrough was found t o be  s t r o n g e r i n the h i g h e r l a t i t u d e s . o b s e r v a t i o n of another  component o f P c 3 b e l i e v e d t o  i n s i d e t h e p l a s m a s p h e r e , w h i c h was exist  This i s contrary to  at the h i g h e r l a t i t u d e s .  only vaguely  proposed.  up  t o now,  available  at a lower  i n the course  experiments  must be  seen t o  previous  b e e n c o n s i s t e n t .'with t h e  I t i s r e g r e t a b l e , h o w e v e r , t h a t no  taneously recorded  originate  Thus, a l l e x p e r i m e n t a l  r e s u l t s on P c 3 m i c r o p u l s a t i o n r e p o r t e d i n t h e c h a p t e r s has,  the  latitude  data  simul-  s t a t i o n have b e e n  of t h i s i n v e s t i g a t i o n .  performed to determine  model proposed i n t h i s t h e s i s i s v a l i d  model  Further  whether  i n the  low  the latitudes,  o r w h e t h e r i t i s a phenomenon a p p l i c a b l e o n l y i n t h e  high-  and m i d - l a t i t u d e s . Future simultaneous t h a t may  be  I n v e s t i g a t i o n s h o u l d be w h i s t l e r data,  available,  p l a s m a p a u s e may  be  as w e l l  planned  as any  to look  satellite  data  so t h a t t h e e x a c t p o s i t i o n o f  the  So f a r , , w h i s t l e r  observations  nave boon t h e most s u c c e s s f u l i n l o c a t i n g t h e  plasmapause.  I f the dimension  located.  at  as w e l l as t h e c o n f i g u r a t i o n o f  p l a s m a p a u s e c a n be  a c c u r a t e l y determined,  o f t h e p l a s m a s p h e r e and may  be  estimated.  the  then the  t o a l e s s e x t e n t the  F u r t h e r , i f the p a r t i c l e  dimension  plasmatrough density  d i s t r i b u t i o n i n t h e m a g n e t o s p h e r e w h i c h a g a i n may  be  estimated  simple  f r o m t h e w h i s t l e r d a t a i s a l s o known, a  o r d e r o f m a g n i t u d e c a l c u l a t i o n b a s e d on t h e  standing  poloidal oscillation  r e s o n a t o r s 'would  i n both hydro-magnetic  176  enable one t o e s t i m a t e the d i u r n a l v a r i a t i o n of t i o n frequency  micropulsa-  to be observed at a g i v e n s t a t i o n .  t u r n , c o u l d be compared w i t h e x p e r i m e n t a l I f the v a l i d i t y of the model may s i n c e a Pc3 i s observed e v e r y day,  This, i n  observation.  indeed be e s t a b l i s h e d ,  continuous  observation  over a network of s t a t i o n s s e l e c t e d a l o n g a geomagnetic meridian could provide continuous  i n f o r m a t i o n on  d i m e n s i o n and the c o n f i g u r a t i o n of the d a y s i d e the plasmasphere and the plasmatrough.  the  plasmapause,  Furthermore,  the  p a r t i c l e d e n s i t y d i s t r i b u t i o n i n s i d e the magnetosphere be  may  estimated. The  e x i s t e n c e of e i g e n o s c i l l a t i o n s i n the magneto-  sphere has been assumed t h r o u g h o u t t h i s t h e s i s . attempt, however, has been made t o study the  No  serious  generation'  mechanism r e s p o n s i b l e f o r the e x c i t a t i o n of such o s c i l l a t i o n s . A t k i n s o n and Watanabe (1966) have suggested t h a t hydromagnetic i n s t a b i l i t y of the K e l v i n H e l m h o l t z type may waves i n the magnetopause which may  generate  surface  be r e s p o n s i b l e f o r the  e x c i t a t i o n of e i g e n o s c i l l a t i o n s i n the o u t e r magnetosphere, which i n t u r n are r e s p o n s i b l e f o r the Pc5 p u l s a t i o n observed at ground s t a t i o n s . between two  S i n c e the plasmapause i s a boundary  ' f l u i d s ' of d i f f e r e n t p a r t i c l e d e n s i t y , i t would  not be too s u r p r i s i n g i f hydromagnetic i n s t a b i l i t y were r e s p o n s i b l e f o r the e x c i t a t i o n of s u r f a c e waves a t the plasmapause, which i n t u r n c o u l d produce o s c i l l a t i o n s i n the plasmasphere and the p l a s m a t r o u g h .  177  The  sudden enhancement o f the  activity following  an  C h a p t e r IV, may  t a k e n as e x p e r i m e n t a l  s u p p o r t s the paragraph.  be  theoretical  A future a detailed  line  be  very  p a i r of  investigation to  should  see  plasmapause.  and  reported  i n the  such a  also give  w h e t h e r Pc4  be  in particular,  e x a m i n e d more  Pc3  may  the  can  be  Pc4  bands, can  last  suggestion. p r i o r i t y to  indeed the  polarization  polarization  of each  should  polarization  generation  mechanism of  the  of  also conjugate Only  of each of  u n d e r s t o o d . Such p r e c i s e  w o u l d a l l o w one. t o p i n p o i n t  be  field  e s t a b l i s h e d f o r comparison.  the  p u l s a t i o n a c t i v i t i e s be  that  planned  r e w a r d i n g , p a r t i c u l a r l y when a m i d - l a t i t u d e stations  in  closely.  bands observed i n m i d - l a t i t u d e s  v/ith p r e c i s e knowledge of the Pc3  given  a h y d r o m a g n e t i c wave p r o p a g a t e d a l o n g  should  three  Pc3  observation  v a l i d i t y of  A c l o s e e x a m i n a t i o n of the the  intensity,  consideration  I n t o the  s t u d y o f Pc4  at the  o f Pc4  i n Pc4  bands of  U n d o u b t e d l y f u t u r e e x p e r i m e n t s must be  t o l o o k more c l o s e l y  c a u s e d by  increase  two  the  these  knowledge  p a r t i c u l a r mode, o r  c o m b i n a t i o n o f d i f f e r e n t modes, o f h y d r o m a g n e t i c o s c i l l a t i o n responsible  for their  excitation.  BIBLIOGRAPHY  A n g e r a m i , J . 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J . a n d H e i r t z l e r , N a t u r e , 210, 361  Hirasawa,  J . R. (1966)  T. a n d N a g a t a , T. (1966) P u r e A p p l . G e o p h y s . , 65, 102  H o l m b e r g , E. R. R. ( 1 9 5 1 ) Ph. D. T h e s i s , U n i v . o f L o n d o n H o l m b e r g , E. R. R. (1953) M. N. R o y a l A s t r o n o m i c a l S o c . , 6 (8), 467 Jacobs  e t a l (1964) J . G e o p h y s . R e s . , 62 ( l ) , 180  J a c o b s , J . A. a n d S i n n o , R. (i960) J . G e o p h y s . R e s . , 65 ( l ) , 107 J a c o b s , J . A. a n d Watanabe, T. (1964) J . Atmos. T e r r . P h y s . , 26, 825 J a c o b s , J . A. a n d W r i g h t , C. S. (1965) Can. J . P h y s . , 43, 2099 K a t o , Y. a n d S a i t o , T. (1959) J . Geomag. G e o e l e c ,  10, 221  K a t o , Y. a n d Watanabe, T. (1956a) S c i . R e p t . T o h o k u U n i v . , S e r . 5, G e o p h y s . , 8, 19 K a t o , Y. a n d Watanabe, T. (1956b) S c i . R e p t . T o h o k u U n i v . , S e r . 5, G e o p h y s . , 8, 157 K a t o , Y. a n d S a i t o , T. (1962) J . Phys. Soc. Japan,  17_, S u p p l . A . I I , 34  l8o K a t o , Y. (1964) Symposium o n U.L.F. E l e c t r o m a g n e t i c F i e l d , Boulder, Colorado. K o p y t e n k o Y u . A. a n d R a s p o p o v , 0. M. (1968) C o s m i c R e s e a r c h , 6 ( 4 ) , 617 K o p y t e n k o Y u . A. a n d R a s p o p o v , 0 . M. (1968) Cosmic R e s e a r c h , 6 ( 4 ) , 6 l l Lawrence  e t a l (1965) A m e r i c a n GeoDhys. U n i o n M e e t i n g , W a s h i n g t o n , A p r i l , 1965  D.C.  L o k k e n , J . E. (1964) N a t u r a l E l e c t r o m a g n e t i c Phenomena b e l o w 30 K c / S P l e n u m P r e s s , New Y o r k M a i n s t o n e , J . S. (1967) N a t u r e , 21^, 5105 M a o l e , E. (1959) J. G e o p h y s . R e s . , 64, 1395 M e l d r u m , R. D. a n d G i b b s , C. A. (1968) D.R.E.P. T e c h n i c a l Memorandum, 68-10 M c N i c o l , R. W. E. a n d M a i n s t o n e , J . S. (1963) A u s t r a l . J . P h y s . , 16, 507 N a g a t a e t a l (1966) P r e s e n t e d a t I n t e r U n i o n Symposium on S o l a r T e r r e s t r i a l Physics, Belgrade N a g a t a , T. a n d F u k u n i s h i , H. (1968^ G e o p h y s . J . R. A s t r . S o c . , 1^, Nishida,  69  A. (1966)  J.. Geophys. R e s . , 2 , ( 2 3 ) , 5669 O b a y a s h i , T. (I965) J.  G e o p h y s . R e s . , JO  (5),  I O 6 9  O b a y a s h i , T. a n d J a c o b , J . A. (1958) G e o p h y s . J . R. A s t r . S o c , JL, 53 P o p e e t a l (1962) J . G e o p h y s ; R e s . , 6 2 , 3588 S a i t o , T. (1964a) Rep. I o n o s p h . S p a c e . R e s . J a p a n , 18, 197 S a i t o , T. (1964b) J . Geomag. G e o e l e c t . , 1,6,  115  181  S a i t o , T. (1966) ESSA, T e c h n i c a l Rep. IER15 - ITSA15 S a i t o , T. (1967) J . Geophys. Res., J_2 ( 1 5 ) ,  3895  S i e b e r t , M . (1964) P l a n e t . Space S c i . , 12, 137 Shchepetuon, R. V. (1966) Geomag. I Aeron. S i s c o e , G. L. e t a l (1969) J . Geophys. Rev., 74 ( 7 h 1759 Snyder, G. W. e t a l (1963^ J . Geophys. Res., 1.8, 1361 S t u a r t , W. F . and Usher, M . J . (1966) Geophys. J . R. A s t r . Soc., 12, 71 T r o i t s k a y a , V. A. (1967^ Solar - T e r r e s t r i a l  P h y s i c s , Academic Press  Veldkamp, J . ( i 9 6 0 ) J . Atmosph. T e r r e s t . Phys., 17_, 320-324, V o e l k e r , H . (1967) Communication presented i n Symposium Watanabe,  1  Birkeland  T. (1965) J . Geophys. Res., JO ( 2 3 ) , 5839  Weaver, J . T. (1963) Can. .J. Phys., 4 l , 484 Weir, R. C. (1966) P.N.L. T e c h n i c a l Memorandum, 66-2 Wentworth, R. C. (1966) J . Geomag. Geoelec., 18 (2), 257 Westphal, K. 0 . and Jacobs, J . A. (1962) Geophys. J . R. A s t r . S o c , 6, 360 Wilson, C.R. (1963) Univ. o f A l a s k a S c i e n t i f i c Report No. 3, AFCRL - 63 - 605 Yanagihara, K. (1959) J . Geomag. Geoelect., JLO, 172 Zybin, K. Yu. (1967) I n d i a n J . Meteorology and Geophys., 18, 349  132  SUPPLEMENT  Carovillano, .Blnsack,  TO  BIBLIOGRAPHY  R. L . and M c C l a y , J. P. \xvop P h y s . F l u i d s , 8 , 2006  J . II. (1967) J . Geophys. Res., 72,  Dungey, J . W.  5231  (1964) Pennsylvania State University. Ionospheric R e s e a r c h L a b o r a t o r y S c i e n c e R e p o r t No. 69  .Kato, Y. and Watanabe, T. (1957) S c i . Rep. T o h o k u U n i v .  Ser.5,  Geophys., 8,  Radoski,  H. R. and C a r o v i l l a n o , R. L . ( 1 9 6 6 ) P h y s . F l u i d s , 9 , 285  Radoski,  II. R. (1967) J . Geomag. G e o e l e c ,  Saito,  T.  (I960) S c i . Rep. T o h o k u U n i v . ,  T e p l e y . and Wontv-jorth (1962) J . Geophys. Res., 67, Trussell,  19,  D.  157  1 S e r 5,  Geophys., 12,  3317  (1966) U n i v e r s i t y of B r i t i s h Columbia, B.Sc. T h e s i s  Geophysics  106  183  APPENDIX CHARACTERISTICS  Using  w h i s t l e r data  d u r i n g J u l y and  made by  THE  PLASMAPAUSE  obtained  a t E i g h t s and  p a r t o f A u g u s t 1963,  a b l e t o deduce the Observation  OF  1  Carpenter  of knee e f f e c t s by  satellite  (Gringduz  observations  with r e s u l t s obtained The  has  knee.  Taglar  Results obtained  were f o u n d t o be  was  a l s o been  et a l , i960;  e t a l , 1965j L a w r e n c e e t a l , 1 9 6 5 ) .  a.  (1966)  f o l l o w i n g b a s i c f e a t u r e s of the  various observers  satellite  Byrd  by  i n good a g r e e m e n t  using w h i s t l e r data.  knee i s a permanent f e a t u r e o f  the  magnetosphere. b.  For c o n d i t i o n s of moderate magnetic a g i t a t i o n w i t h Kp =  2 - 4,  the c o n f i g u r a t i o n of  plasmapauge i n the e q u a t o r i a l p l a n e i n F i g . 1.2  a f t e r Carpenter  (i)  i s displayed  (1966).  p r i n c i p a l f e a t u r e of t h i s curve  are  the  The as f o l l o w s :  A r e l a t i v e l y b r o a d minimum i n g e o c e n t r i c distance, centered  roughly  on 0600  L.T.,  t h e minimum d i s t a n c e i s a b o u t 3 - 3.5 (ii)  A maximum g e o c e n t r i c d i s t a n c e 2000 L.T.,  (iii)  t h e maximum b e i n g  at  a decrease i n the  g  about,  a b o u t 5 - 5.55  F o l l o w i n g t h e maximum n e a r 2000 L.T., is  R.  there  r a d i a l d i s t a n c e of  p l a s m a p a u s e on t h e n i g h t  s i d e of the  the  earth.  R,  The  decrease I s roughly  the  order  1.6  R  over a period of  o f 10 h o u r s ,  (iv) A rapid increase  i n radial distance  n e a r 1300 L.T.  i n v o l v i n g a v a r i a t i o n o f about 1 of about 1 hour. hours before  i n a period  T h i s e f f e c t may o c c u r  o r a f t e r l 8 0 0 L.T. w i t h  several  roughly  h a l f o f t h e c a s e s f a l l i n g w i t h i n an h o u r o r two o f 1600 L.T. (v) A g r a d u a l  increase  i n radial distance  on t h e d a y  s i d e f r o m a b o u t 0600 L.T. t o m i d ^ a f t e r n o o n . total  range o f t h i s  0.5 R  by  v a r i a t i o n i s of the order of  and w i t h i n t h e p e r i o d  a s e c o n d a r y maximum  The  there  a p p e a r s t o be  a r o u n d 1200 L.T., f o l l o w e d  a s e c o n d a r y minimum a r o u n d 1400 o r 1500 L.T.  During very (i-^ = 0  quiet p l a n e t a r y magnetic  1)  conditions  t h e above m e n t i o n e d d i u r n a l c u r v e o f t h e  p l a s m a p a u s e moves o u t w a r d and assumes a more  nearly  c i r c u l a r configuration at i t s larger radius.  (The  h i g h - l a t i t u d e p o s i t i o n of Byrd favourable  s t a t i o n becomes  f o r knee o b s e r v a t i o n  (Binsack,  1967)  U n d e r s t o r m y c o n d i t i o n s t h e p l a s m a p a u s e moves and  t h e d e g r e e o f asymmetry w i t h  may become more p r o n o u n c e d 1'364; C a r p e n t e r ,  1962).  respect  ). inward  to the earth  ( C o r c u f f and D e l a r o c h e ,  185  APPENDIX SPECIFICATION  OF  FREQUENCY RANGE:  KAY  2  ELECTRIC  7029A  5 t o 16000 Hz i n s i x ranges; 500 Hz 1000 Hz 2000 Hz  5  10 20 40 80 160 DISPLAYS AVAILABLE:  SONAGRAPH  4000 Hz  8000 Hz 16000 Hz  Frequency-vs-amplitude-vs-time (conventional) Frequency-vs-amplitude-vs-time (contour) Amplitude-vs-frequency Amplitude-vs-time  ANALYSIS TIME:  1.3 M i n u t e s  EFFECTIVE RESOLUTION:  5 10 20 40 80 160  AGC RANGE:  500 Hz 1000 Hz 2000 Hz  4000 Hz  8000 Hz 16000 Hz  2.8 5.6 11.2 22.5 45 90  and 19.0 and 37.5 and 75 and 150 and 300 and 600  Hz Hz Hz Hz Hz Hz  V a r i a b l e 20 t o 40 DB down t o 10.  FREQUENCY CALIBRATION: S w i t e n a b l e a t 50, 500, o r 1000 Hz intervals. RESPONSE: RECORDING TIME:  +2 DB over e n t i r e 5 10 20 -  40 -  500 Hz 1000 Hz 2000 Hz  4000 Hz  80 8000 Hz 160 - 16000 Hz  AMPLIFIER CHARACTERISTICS: INPUT IMPEDANCE:  range. 38.4 19.2 9.6 4.8 2.4 1.2  sec sec sec sec sec sec  F l a t o r 13 DB h i g h - f r e q u e n c y pre-emphasis. 200, 600, o r 10,000 Ohm,  switchable  186  APPENDIX POSSIBILITY  OF  MULTI-BAND  3 P c 3 CAUSED  BY  HARMONICS  S t u a r t and Usher (1966) found t h a t t h e Pc s p e c t r a a t the t h r e e B r i t i s h s t a t i o n s show peaks o f m i c r o p u l s a t i o n o c c u r r e n c e a t 30 sec a t L e r w i c k , 60 sec a t E s k d a l e m u i r and 40 sec a t H a r t l a n d .  A secondary peak a t 25 sec p e r i o d i s  a l s o observed a t E s k d a l e m u i r .  Two p o s s i b l e ways were o f f e r e d  to r e c o n c i l e the d i f f e r e n c e s : (a) There may be no l a t i t u d e dependence o f t h e fundamental p e r i o d o f m i c r O p u l s a t i o n s o c c u r r i n g i n t h i s range, and the d i f f e r e n c e s may t h e n be due t o d i f f e r e n t harmonics a p p e a r i n g a t each station.  I n t h i s way a fundamental p e r i o d might  be 120 second o f which L e r w i c k was the f o u r t h harmonic, H a r t l a n d t h e t h i r d , and E s k d a l e m u i r the second and f i f t h . (b) A l a t i t u d e dependence o f fundamental p e r i o d may e x i s t , b e i n g 40 sec a t H a r t l a n d , 60 sec a t E s k d a l e m u i r and 90 sec a t L e r w i c k .  I n t h i s case  the observed L e r w i c k a c t i v i t y may be t h e t h i r d harmonic, and t h e secondary peak a t E s k d a l e m u i r may be second o r t h i r d  harmonic.  No example, however, has been g i v e n i n S t u a r t and Usher's paper t o show t h e d i u r n a l p a t t e r n s observed a t different  stations.  To c o n s i d e r whether the m u l t i - b a n d s t r u c t u r e d P c 3 observed at R a l s t o n too may  be caused by h i g h e r harmonics  of  a p a r t i c u l a r fundamental f r e q u e n c y , as suggested by S t u a r t and Usher  (1966) mentioned  have c o n s i d e r e d the Let  above or by Mainstone  (1966), we  following:  be the fundamental f r e q u e n c y of a g i v e n s t a t i o n  a t a g i v e n time t . Suppose t h a t o n l y the n t h and the n+m t h harmonics  are  observed at t h a t s t a t i o n at time t of a g i v e n day, t h a t i s •  =  n, t  n  F, t (n+m)  ' n+rn, t  F,  Then the s e p a r a t i o n between the two harmonics observed a t time t i s =  n+m, n  fn+m, t  f  n,t  =  t  raF  At a l a t e r time T, i f the fundamental f r e q u e n c y of the g i v e n s t a t i o n changes t o F^. , s i n c e o n l y a c o n t i n u o u s event +T  i s t o be c o n s i d e r e d , the harmonics observed would f  n,t+T  f ,nd  n+m,  =  t+T  ,t+T n+m, n  n  F  =  t+T v  (n+m)-F ' t+T m F t+T  and the r a t i o „t+T  n+m,t+T 'n+m, n, t  F  t  be  188  which i m p l i e s t h a t as the fundamental f r e q u e n c y (or d e c r e a s e s ) ,  increases  the s e p a r a t i o n between two harmonic bands  should a l s o i n c r e a s e (or I f the m u l t i - b a n d  decrease). s t r u c t u r e d P c 3 observed at  R a l s t o n i s caused by harmonics, i t should behave as p r e d i c t e d above.  However, o b s e r v a t i o n s of F e b r u a r y 11  September 3,  and  (Feb.  III.2b),  October, 1 9 6 7 * f o r example, I n d i c a t e t h a t  t h i s i s not the case.  Thus the e f f e c t of h i g h e r harmonics  alone cannot be r e s p o n s i b l e f o r the e x i s t e n c e of the m u l t i band P c 3 o b s e r v e d .  189  APPENDIX TABLE  OF  THE  K  INDEX  ILLUSTRATED  Jan Apr  21, 18,  1964 1964  June 15, 1965 June 24, 1965 Sept 16, 1965 Sept 18, 1965  1  2  X X  0  1_  2  1  2_  1  + 1_ .  Sept 20, 1965  1  Dec Dec  14, 1965 17,  1965  Dec  19,  1965  22,  1966  Dec  26,  1966  Feb  9,  Feb  10,  1967 1967  Feb  11,  1967  Feb  12,  1967  Feb Feb Feb  17,  1967  23,  1967  24,  1967  4  0  0  + o +  °  X 4_ X X X X 2, T  3_ • 4  0  l_  2  Oo  lo  0  °e  °o 1_  °o  O  X  1_  1_  4_  3_  X X 0  1  0  +  IN  3  +  Sept 19, 1965  Aug  0  o o  2_ 1  0  4  4  0  6  0  0  0  X  \  4  0  i_  4 1  + + +  3_ 2_  0  0 5_  A  X  8  °+ 4_  ° X  5_  4  1  0  X 3, \ 4_ X X 4_ 4_ X X  +  °  T  4 2  + o-  0+  1_  0,  °o  ° 0  °o 1_  ! 1_  2_  2_  3_  2_  2  5_  4_  4  0  3,  1_  0  4_  1_  T  1_  1_  0  ° X 0  0  +  X 4_ X X X °o ° 1_ 1_ X 4.0 \ 3 o X X 2_ X' 0 0 o 1+ 1_ +  0  3  +  i_  0  0 o  +  +  24_  X 35_ 2  3 +  2  5  0  o  2  1-  +  +  P 3  +  1-  4  2  ^  7  0+  X ° 4_  DATES  FIGURES  5  0  FOR  1+  4+  1_  3_ n  o  o  + 1_  3°o 1  0  3  0  2_  3_  1  0  9_  1 4-  3  G  3  +  2  o  4  1  0  0  X  3.  2  3 +  22_  X  19D  K  Date 1  Feb Mar Mar Mar May May Aug Aug Aug Aug  Sept Sept Oct Oct Oct Oct Oct Oct  26,  2  1967  3  is!  1967  26,  1967  1  27,  1967  4_  10,  1967  \  1967  \  22,  9,  1967 1967  24,  1967  1,  2 0  4_  1967 1967  +  \ \ •3_  o  2  3  0  \ 1  o  'l,  1_  1  X  2_  o  X  3_ 3  +  3  0  3  6  5,  1967  2_  4  4  16,  1967  2  13,  1967  2_  1967  Oct  2b,  1967  Oct  29,  1967  o  2  1_  1_  o  4_  \  o  2^  1967  3_  2  Nov  13,  1967  3  Nov  15,  1967  0  G  +  o  o  3  Q  1 0 2  •f  3  G  °+  25_  2_  9_  +  +  2_  +  1_  0  o  +  0  + 1_  4_  2_  1  o  3  1  2_  1 0  o  4  + 13_  15, 2  0  3  0  29 _  2_  1  14  1_  3_  o  4_  0  l  4  0  0  8 0  15_  24  +  1_  2_  2_  1_  1_  3_  1_  1  l_  °  1_  . i_  5_  3,  2^  29 _  1  19_  5  0  3o  6  0  0  2  ^0  o  o  2  0  l_  2 6  5_  2  2  0  2  +  2  o  2_  0  °  4  o  2  1  4  °  3_  2  20_  3_  -'o  4  3  o  \  •5  0  \  2_  2  2_  o  3  K  3  o  2  0  l_  3_  0  +  1  +  5+  o  2  0  +  \  0  +  +  +  1_  1967  o  4  +  0  2  0  0  ° \ ° 3  3_  2  l  o  °  3_  0  +  0 2  3  +  2  +  4_  3_  2  2_  1,-r  1  l_  2  2_  1967  V  5_  O  2_  +  V 2_  0  2_ 0  1_  0  o  2  £ P  8  7  o  T  4-  1967  9,  6  +  +  3  4,  Nov  3,  3o  1  30,  2 +  3  2_  \  Oct  2  0  1967  25,  3_  5  0  7,  12,  o  4  T  23,  25,  1_  3  P  0  +  0  14_  T  0 0  2, T  1  1, T  + 3o 3o  4_  3  0  1_ 0  4_ 3 +  4_ 3  +  18  +  191  Date  Nov Nov Nov Dec Dec Dec  1  2  17, 1967  1_  1  . l o , 1967  1  •  ]_  1_  2_  1967  2_  4  7, 1967  4,  28, 1967  3  4  0  +  1_  5  0 0 1_  0  1967  19,  S K_  V p  L  + T  o  6  0  n  + +  1_ 2_,_ ).  4_  4 0  0,  4_  0  1_  -r  1_  +  7  8  -  p  0  0 0 1  0 0,  0  ^_  1+  1  0 . 0  6  4-  3  0  4 1  0  +  0 +  +  3_  +  4^  2u_  9  27,  . 0 2^  "r  9.  

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