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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., R o y a l Melbourne I n s t , of Technology, 1961 M . S c , The U n i v e r s i t y of B r i t i s h Columbia, 1966 A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY i n the Department of GEOPHYSICS We ac c e p t t h i s t h e s i s as c o n f o r m i n g t o the r e q u i r e d s t a n d a r d THE UNIVERSITY OF BRITISH COLUMBIA November, 1969 In p r e s e n t i n g t h i s t h e s i s in p a r t i a l f u l f i l m e n t o f the r equ i r emen t s f o r an advanced degree at the U n i v e r s i t y o f B r i t i s h C o l u m b i a , I ag ree tha t the L i b r a r y s h a l l make i t f r e e l y a v a i l a b l e f o r r e f e r e n c e and s t u d y . I f u r t h e r agree tha p e r m i s s i o n f o r e x t e n s i v e c o p y i n g o f t h i s t h e s i s f o r s c h o l a r l y pu rposes may be g r a n t e d by the Head o f my Department o r by h i s r e p r e s e n t a t i v e s . It i s u n d e r s t o o d tha t c o p y i n g o r p u b l i c a t i o n o f t h i s t h e s i s f o r f i n a n c i a l g a i n s h a l l not be a l l owed w i t hou t my w r i t t e n p e r m i s s i o n . Department o f The U n i v e r s i t y o f B r i t i s h Co lumbia Vancouver 8, Canada i l ABSTRACT Dynamic s p e c t r a p r o c e s s e d from d a t a r e c o r d e d on magnetic tape a t the m i d - l a t i t u d e R a l s t o n 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 . The Fc3,k p u l s a t i o n s appear t o behave 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 o t h e r o b s e r v e r s at l o w - l a t i t u d e s t a t i o n s . The v a r i a t i o n of the Pc3,k 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 an o t h e r , the 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 of magnetic d i s t u r b a n c e r e p r e s e n t e d by the Kp-index. I t appears, however, t h a t most of the Pc3,k s p e c t r a a n a l y s e d may be c l a s s i f i e d i n t o one o f , o r a c o m b i n a t i o n o f , f o u r 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 s t e a d y 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 the f i n e s t r u c t u r e of thes e f o u r d i u r n a l p a t t e r n s . The cr u x o f the p r e s e n t i n t e r p r e t a t i o n i s t h a t R a l s t o n , under moderate magnetospheric 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 the plasmasphere and/or the p l a s m a t r o u g h depending 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 of 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 ) i n the s e two magnetospheric r e g i o n s are c o n s i d e r e d t o be the prime s o u r c e s of the ground observed Pc3*4 magnetic p u l s a t i o n s . Such s u g g e s t i o n i s r e i n f o r c e d by o b s e r v a t i o n s made s i m u l t a n e o u s l y a t o t h e r mid- and h i g h - l a t i t u d e s t a t i o n s . Other m o r p h o l o g i c a l p r o p e r t i e s of Pc3 and Pc4 are d i s c u s s e d i n the l i g h t of the new i n t e r p r e t a t i o n . i i i TABLE OP CONTENTS PAGE ABSTRACT i i LIST OP FIGURES v i LIST OP TABLES x i ACKNOWLEDGEMENTS x i i CHAPTER I GENERAL INTRODUCTION 1 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 System 22 11.3 Tape A n a l y s i n g System 26 CHAPTER I I I SUBCLASSIPICATION OP Pc3 IN MID LATITUDE - DIURNAL VARIATION OF PC3 FREQUENCY AT RALSTON 29 111.1 I n t r o d u c t i o n 29 111.2 M u l t i - B a n d S t r u c t u r e d C o n t i n u o u s P u l s a t i o n 33 111.3 Normal Type w i t h Morning and A f t e r n o o n S e p a r a t i o n s 4-2 111.4 The I n v e r t e d U-Type w i t h D i s c r e t e S t r u c t u r e 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 M i s c e l l a n e o u s Types 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 D i s c u s s i o n 75 i v CHAPTER IV Kp-DEPENDENCE OP Pc3 IN MID LATITUDES 83 IV.1 I n t r o d u c t i o n ^ 83 IV.2 Kp-Dependence o f the Pc3 Frequency 86 IV.3 Sudden Enhancement o f Pc3 A c t i v i t y 101 IV. 4 D i s c u s s i o n 106 CHAPTER V COMPARATIVE STUDIES OP Pc3 IN HIGH AND MID LATITUDES 110 V. l I n t r o d u c t i o n 110 V.2 L a t i t u d e Dependence o f Pc3 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 R a p i d -Run Magnetograms 115 V.3 D i u r n a l V a r i a t i o n o f Pc3 a t a Hig 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 (Geomagnetic <f) = 66.6°, L=7.5) 122 V.4 L a t i t u d e Dependence o f Pc3 Frequency 132 V.5 Conjugacy o f Pc3 a t H i g h and M i d -L a t i t u d e 144 V. 6 D i s c u s s i o n 150 CHAPTER V I GENERAL STUDIES OF Pc4 I56 V I . 1 I n t r o d u c t i o n 156 VI.2 D i u r n a l V a r i a t i o n o f Pc4 a t the M i d - L a t i t u d e R a l s t o n S t a t i o n 159 VI.3 L a t i t u d e Dependence o f Pc4 166 VI.4 D i s c u s s i o n 172 CHAPTER V I I POSTSCRIPT: DISCUSSION AND FUTURE EXPERIMENT 174 V BIBLIOGRAPHY APPENDICES: Appendix 1 Appendix 2 Appendix 3 Appendix 4 C h a r a c t e r i s t i c s o f t h e Plasmapause 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 7029A P o s s i b i l i t y o f M u l t i - B a n d Pc3 Caused by Harmonics T a b l e of t h e K Index f o r Dates I l l u s t r a t e d i n ^ F i g u r e s 178 I 8 3 I85 186 189 LIST OP FIGURES CHAPTER I FIG 1.1 PIG 1.2 FIG 1.3 CHAPTER I I PIG I I . l a FIG I I . 2 a II.2b CHAPTER I I I FIG I I I . 2 a I I I . 2 b I I I . 2 c I I I . 2 d I I I . 2 e PIG I I I . 3 a M a g n e t o s p h e r i c F i e l d L i n e C o n f i g u r a t i o n E q u a t o r i a l A l f v e n V e l o c i t y o f the Magnetosphere 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 the p l a s -matrough on Magnetic A c t i v i t y ( a f t e r T r u s s e l , 1966) S t a t i o n s f rom which Magnetograms were Obtained Frequency Response o f the PM B r o a d -Band R e c o r d i n g System F M - M i c r o p u l s a t i o n R e c o r d i n g System 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 of Pc3 R a l s t o n Y, Feb. 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 Frequency from Dawn t o Dusk R a l s t o n Y, Feb. 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 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 M o r n i n g R a l s t o n X, Dec. 6, 1967 4 bands s t r u c t u r e d Pc3*^ R a l s t o n X, Oct. 18, 1967 Normal Type w i t h Morning and A f t e r n o o n S e p a r a t i o n v i i F I G I I I . 3 b R a l s t o n X, Dec. 7, 1967 Normal Type under. D i s t u r b e d C o n d i t i o n s 47 I I I . 3 c R a l s t o n X, Feb. 10, 1967 Normal Type under Q u i e t C o n d i t i o n s 48 I I I . 3 d R a l s t o n X, Oct. 30, 1967 A f t e r n o o n Type o f Pc3 49 I I I . 3 e R a l s t o n X, Mar. 19, 1967 The 'Pause' t h a t Observed i n the Morning 50 FIG I I I . 4 a R a l s t o n X, Mar. 26, 1967 I n v e r t e d U-Type w i t h D i s c r e t e S t r u c t u r e 52 I I I . 4 b R a l s t o n X, Dec. 28, 1967 I n v e r t e d U-Type w i t h D i s c r e t e S t r u c t u r e 53 FIG I I I . 5 a R a l s t o n X, Oct. 16, 1967 I n v e r t e d U-Type w i t h D i f f u s e d S t r u c t u r e 57 I I I . 5 b 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 I I I . 5 c 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 Secondary Maxima 59 FIG I I I . 6 a R a l s t o n X, S e p t . 7, 1967 C o m b i n a t i o n o f the D i s c r e t e I n v e r t e d U-Type and the Morning and A f t e r n o o n Type 65 I I I . 6 b R a l s t o n X, Oct. 4 , 1967 Mixed 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 I I I . 6 c R a l s t o n X, Oct. 26, 19.67 Mixed 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 I I I . 6 d R a l s t o n X, Oct. 25, 1967 Mixed I n v e r t e d U-Type and Normal Type 63 I I I . 6 e R a l s t o n X, S e p t . 1 , 1 9 6 7 M i x t u r e o f a l l 4 b a s i c t y p e s 69 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 I V P I G I V . 2 a I V . 2 b I V . 2 c I V . 2 d I V . 2 e I V . 2 f I V . 2 g . P I G I V . 3 a I V . 3 b I V . 3 c C H A P T E R F I G V V . 2 a V . 2 b V . 2 c R a l s t o n X , F e b . 23, 19^7 M i s c e l l a n e o u s T y p e s R a l s t o n X , O c t . 12, 1967 M i s c e l l a n e o u s T y p e s R a l s t o n X , M a r . 18, 1967 M i s c e l l a n e o u s T y p e s R a l s t o n X , O c t . 29, 1967 M i s c e l l a n e o u s T y p e s £ l C D e p e n d e n c e o f t h e P c 3 M e a n p F r e q u e n c y K p D e p e n d e n c e a t R a l s t o n 0 = 5 8 . 8 ° R a l s t o n X , N o v . 18, 1967 ^ = 0 R a l s t o n X , M a y , 10, 1967 " P - 1 R a l s t o n X , O c t . 5, 1967 R a l s t o n X , M a r . 27, 1967 . * P -3 R a l s t o n X , D e c . 26, 1966 R a l s t o n X , A u g . 9, 1967 N o S u d d e n E n h a n c e m e n t o f P c 3 R a l s t o n X , M a y 22, 1967 S u d d e n E n h a n c e m e n t o f P c 3 R a l s t o n X , A u g . 23, 1967 S u d d e n E n h a n c e m e n t o f P c 3 a n d P c 4 D e c e m b e r 17, 1965 = 0 + F e b r u a r y 17, 1967 K p = 3 Q P c 3 M o d u l a t e d P e l , G r e a t W h a l e X , A u g u s t 2 2 , 1966 71 72 73 74 94 95 96 97 98 99 1 0 0 103 1 0 4 105 119 1 2 0 1 2 1 D i u r n a l R e gions a t G r e a t Whale Great Whale-, September 20, 1965 P o s i t i v e Bay A s s o c i a t e d Pc2,3 Great Whale, December 19, 1965 N e g a t i v e Bay A s s o c i a t e d P c 2 ,3 September 18, 1965, I m p u l s i v e E v e n t s J a n u a r y 21, 1964, L a t i t u d e Dependenc o f P c 3 , 4 A p r i l 18, 1964, Pc5 w i t h Pc3 R i d e r s M u l t i - b a n d S t r u c t u r e d Pc3 M u l t i - b a n d S t r u c t u r e d Pc3 October 18, 1967, L a t i t u d e Dependenc o f Normal Type o f Pc3 September 19, 1965, Pc3 a t t h e M i d - L a t i t u d e s F e b r u a r y 26, 1967, S i m u l t a n e i t y o f the I n v e r t e d U-Type o f Pc3 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 Conjugacy o f Pc3 Conjugacy o f Dawn and Dusk Type Pc 2,3 September 16, 1965, Conjugacy o f Pc3 a t Hig h and Mid L a t i t u d e s Conjugacy under D i s t u r b e d C o n d i t i o n s 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 Occurrence o f Pc3 and Pc4 R a l s t o n X, November 13, 1967 Pc4 i n the A f t e r n o o n X FIG VI.2d Comparison o f t h e X and Y F i e l d Components 165 FIG VI.3 a Pg A c t i v i t y a t M c G i l l 169 VI.3b Conjugacy and L a t i t u d e Dependence of Pc4 170 VI.3c L a t i t u d e Dependence o f Pc's 171 x i L I ST OP TABLES TABLE PAGE 1.1 C l a s s i f i c a t i o n o f M i c r o p u l s a t i o n s 2 11.1 The L o c a t i o n and Magnetic E l e m e n t s of S t a t i o n s f r om which Data was Made A v a i l a b l e 19 11.2 S e l e c t e d Data Used i n t h e P r e s e n t I n v e s t i g a t i o n 20-21 111.1 C h a r a c t e r i s t i c s of C l e a r M u l t i - B a n d C o n t i n u o u s P u l s a t i o n a t R a l s t o n i n 1967 35 111.2 Dates 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 55 111.3 S u b - C l a s s i f i c a t i o n o f Some Pc3 E v e n t s 62-64 IV.1 Dependence o f D i u r n a l V a r i a t i o n P of Pc3 87-88 V . l L a t i t u d e Dependence o f Pc3 R e p o r t e d by Data Observer 155 x i i AC KNOWLBDGEMENTS I wish 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. Watanab f o r h i s p a t i e n t s u p e r v i s i o n , g u i d a n c e , and e n c o u r a g e m e n t , an f o r many h o u r s o f d i s c u s s i o n d u r i n g t h e c o u r s e o f t h e i n v e s t i g a t i o n . I am d e e p l y i n d e b t e d t o h i m ' f o r many v a l u a b l s u g g e s t i o n s , c r i t i c i s m s , and comments and f o r c a r e f u l r e v i e w i n g o f t h e m a n u s c r i p t . I a l s o w i s h t o t h a n k D r . J . A. J a c o b s and more r e c e n t l y D r . R. D. R u s s e l l f o r t h e i r c o n s t a n t i n t e r e s t and e n c o u r a g e m e n t and f o r p r o v i s i o n o f an a t m o s p h e r e c o n d u c i v e t c s t u d y and r e s e a r c h . 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 o f D r . J . K. P e t r i e i n h e r c a r e f u l r e v i e w i n g o f the m a n u s c r i p t . I. w o u l d l i k e t o t h a n k D r . R. M. E l l i s f o r a r r a n g i n g t h e u s e o f t h e S a n b o r n t a p e r e c o r d e r . I am d e e p l y i n d e b t e d t o t h e D e f e n c e R e s e a r c h E s t a b l i s h m e n t , P a c i f i c f o r p r o v i d i n g d a t a as w e l l a s e q u i p m e n t e s s e n t i a l t o t h i s i n v e s t i g a t i o n . I n p a r t i c u l a r , I am most g r a t e f u l t o S i r C h a r l e s W r i g h t , Mr. A. Shand, D r . K. C. M a c l u r e , and Mr. C. Gibbs o f t h e D.R.E.P. who have g i v e n so much o f t h e i r t i m e and a s s i s t a n c e t o make t h i s i n v e s t i g a t i o n p o s s i b l e . T h a n k s a r e due t o D r . D. S m y l i e and D r . T. U l r y c h f o r t h e i r h e l p f u l comments i n t h e f i n a l p r e p a r a t i o n o f t h e m a n u s c r i p t . H e l p f u l d i s c u s s i o n s are acknowledged w i t h my c o l l e a g u e s , i n p a r t i c u l a r , M e s s r s . K. R. Roxburgh, M. B e r r e t t a , R. M i c h k o f s k y and R. Olowin. T h i s s t u d y was p a r t i a l l y s u p p o r t e d by a r e s e a r c h g r a n t p r o v i d e d by the N a t i o n a l R e s e a r c h C o u n c i l of Canada t o Dr. T. Wa'tanabe. CHAPTER I GENERAL INTRODUCTION At the 13th General Assembly of the I n t e r n a t i o n a l Union of Geodesy and Geophysics i n Berkeley, August 1963, 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 micropul-s a t i o n s were discussed 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. Prom the experimental knowledge obtained since the I n t e r n a t i o n a l Geophysical Year, i t has been recognized that micropul-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 : those of a r e g u l a r , and mainly continuous, character and those with an i r r e g u l a r p a t t e r n (Jacobs et a l , 1964). The 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 Table 1.1. The research to be presented i n t h i s t h e s i s i s p r i n c i p a l l y concerned with the Pc3 ,4 band of continuous m i c r o p u l s a t i o n s . Since great advances have been made i n the past f i v e years i n the f i e l d of m i c r o p u l s a t i o n research and i n I t s 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 course, be improved. In p a r t i c u l a r , a b e t t e r understanding of the general p h y s i c a l state of the magnetosphere and of the morphological 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 enables one to define more a c c u r a t e l y the range of periods f o r a number of groups. For. Instance, i t i s now a well-known f a c t that 2 there e x i s t many d i f f e r e n t types of p u l s a t i o n s w i t h i n the frequency range d e f i n i n g the P e l group. T h i s enables one to s u b c l a s s i f y P e l a c c o r d i n g l y ( S a i t o , 1964a; T r o i t s k a y a , 1967j e t c . ) . TABLE I.1 CLASSIFICATION OF MICROPULSATIONS Type Range of P e r i o d s (Sec) , f (mHz) Continuous P u l s a t i o n s P e l 0.2 - 5 200 - 5000 Pc2 5 - 1 0 100 - 2000 Pc3 1 0 - 4 5 22 - 100 Pc4 45 - 150 6.7 22 Pc5 150 - 600 1.7 6.7 I r r e g u l a r P u l s a t i o n s P i l 1 - 40 25 - 1000 Pi2 40 - 150 6.7 25 The Pc3,4 bands of continuous m i c r o p u l s a t i o n s represent one of the o l d e s t and yet the l e a s t known f i e l d i n m i c r o p u l s a t i o n r e s e a r c h . Eschenhagen observed p u l s a t i o n s with a p e r i o d of about 30 seconds at Potsdam, Germany as e a r l y as 1896 (Kato and Watanabe, 1957b), but i t was not u n t i l very r e c e n t l y , mainly due to the r e s e a r c h momentum gathered since the IGY, th a t some of the morp h o l o g i c a l p r o p e r t i e s of Pc3,4 became b e t t e r known. Even today, when n e a r l y a decade has elapsed s i n c e the epoch 3 of space e x p l o r a t i o n , some of the important p r o p e r t i e s of Pc3,4 such as the d i u r n a l v a r i a t i o n of frequency, l a t i t u d i n a l , l o n g i t u d i n a l and K -dependence, e t c . , remain a matter of controversy. Prom time to time apparently c o n t r a d i c t o r y r e s u l t s have been reported by d i f f e r e n t experimenters and there i s not yet a c o n s i s t e n t model that could e x p l a i n these d i f f e r e n c e s . The s c a r c i t y of s u f f i c i e n t l y high q u a l i t y data and the inadequacy of the s p e c t r a l a n a l y s i s techniques employed have been recognised as two p r i n c i p a l reasons f o r the existence of some of the i n c o n s i s t e n c i e s . Although chart magnetograms have y i e l d e d so much i n f o r m a t i o n i n the past and w i l l continue to do so i n the f u t u r e , s c a l i n g of chart-recorded magnetograms may o f t e n be misleading p a r t i c u l a r l y when more than one frequency component i s in v o l v e d . Various s p e c t r a l a n a l y s i n g techniques have been developed r e c e n t l y i n m i c r o p u l s a t i o n research, one of the most s u c c e s s f u l being dynamic spectrum a n a l y s i s of magnetic tape-recorded data, used, f o r example, i n the disc o v e r y of hydromagnetic emissions ( S a i t o , i960; Tepley and Wentworth, 1962). In the past three years t h i s new s p e c t r a l a n a l y s i n g technique has been extended to many other lower frequency regions. Hirasawa and Nagata (1966), and Nagata and Fukunishi (1968) among others, were s u c c e s s f u l i n producing dynamic spectra of Pc3,4 and they observed a c e r t a i n r e g u l a r i t y 4 i n the d i u r n a l v a r i a t i o n of frequency i n each of these bands. Their r e s u l t s , however, are based only on an a n a l y s i s of magnetic data from l o w - l a t i t u d e s t a t i o n s . As discussed i n Chapter I I I , dynamic spectra processed from magnetic tapes recorded at the m i d - l a t i t u d e R a l s t o n s t a t i o n (Alberta) i n 1967 have been studied i n d e t a i l . More than 500 sonagrams have- been stu d i e d , and the Kay E l e c t r i c Sonagraph 7029 with scale expander provides a marked improvement i n the q u a l i t y of these sonagrams. The r e s u l t s i n d i c a t e that Pc3 ,4 observed i n m i d - l a t i t u d e s behaves i n a much more complicated manner than reported by Hirasawa and Nagata (1966) at the 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 Pc3 ,4 frequency at Ralston assumes d i f f e r e n t forms from one day to another, the 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 general l e v e l of magnetic disturbance represented by the K^-index. I t appears, however, that most of the Pc3 ,4 spectra analysed may be c l a s s i f i e d i n t o one of, or a combination of, four w e l l - d e f i n e d d i u r n a l patterns 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 to e x p l a i n the existence as w e l l as the f i n e s t r u c t u r e of these four 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 to be of magnetospheric o r i g i n , the morphology of Pc3,4 cannot be understood without a knowledge of the s t r u c t u r e and the 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 important f i n d i n g s i n the past f i v e .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 research i s the dis 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 that 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 abrup t l y by two orders of magnitude at a r a d i a l distance of s e v e r a l e a r t h r a d i i . This abrupt d e n s i t y decrease, which was designated 'knee' by Carpenter and i s now a l s o known as the 1plasmapause 1, was l a t e r found to be a r e g u l a r three-dimensional feature of the magnetosphere (Carpenter, 1966; Angerami and Carpenter, 1966). . The plasmapause d i v i d e s the magnetosphere i n t o two regions, namely, the plasmasphere (the inner 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 con-f i g u r a t i o n has been reported by Carpenter. I t has been found that 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 pl a n e t a r y magnetic c o n d i t i o n s represented by the value of the Kp-index. The general p r o p e r t i e s of the plasmapause as reported by Carpenter are described i n Appendix 1. Carpenter's d e s c r i p t i o n of the general p h y s i c a l p r o p e r t i e s of the magnetosphere has profoundly a f f e c t e d the model to be chosen to 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 reported i n t h i s t h e s i s . 6 .' ' Both- the A l f v e n v e l o c i t y i n the e q u a t o r i a l r e g i o n and the e s t i m a t e d f u n damental e i g e n - p e r i o d f o r each f i e l d l i n e 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 q u a t o r i a l e l e c t r o n d e n s i t y d i s t r i b u t i o n t h a t t a k e s i n t o account th e p resence of the plasmapause. A d i p o l e f i e l d i s assumed i n the p r e s e n t c a l c u l a t i o n , and the e l e c t r o n d e n s i t y d i s t r i b u t i o n a l o n g magnetic f i e l d l i n e s of f o r c e i s t a k e n t o be p r o p o r t i o n a l t o a c e r t a i n power n (n = 1 i s assumed) of the i n t e n s i t y of the l o c a l magnetic f i e l d o f the e a r t h f o l l o w i n g Watanabe (1965), Wentworth (1965), B r i c e (1965), and o t h e r s . The r e s u l t i s summarized by a graph shown i n P i g . 1.2. Under the a ssumption t h a t m i c r o p u l s a t i o n s are due t o resonance i n the d i f f e r e n t p o r t i o n s of t h e E a r t h ' s magnetic c a v i t y , one might e x p e c t t h a t m i c r o p u l s a t i o n s g e n e r a t e d and/or propagated i n s i d e each c a v i t y bounded by the A l f v e n v e l o c i t y maxima c o u l d c h a r a c t e r i z e d i f f e r e n t p h y s i c a l p r o p e r t i e s o f each of t h e s e r e g i o n s . The g e n e r a l problem of resonances i n a c o n f i n e d plasma magnetized by a d i p o l e f i e l d i s m a t h e m a t i c a l l y ponderous (Dungey, 1954; C a r o v i l l a n o and McClay, 1965). 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 the 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 r e c e i v e d more a t t e n t i o n . I t i s found t h a t t h i s symmetry r e q u i r e -ment produces a s i g n i f i c a n t d e c o u p l i n g of the v e c t o r wave 7 equation 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 represented by the azimuthal component of the perturbed v e l o c i t y / and the p o l o i d a l mode i s represented by the same component of the perturbed 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 the two modes i s that the energy of the t o r o i d a l mode i s guided along the f i e l d l i n e and so should be s t r o n g l y latitude-dependent whereas the p o l o i d a l mode should not. Many authors have t r e a t e d the t o r o i d a l mode under various assumptions concerning the plasma d e n s i t y (Kato and Watanabe, 1956; Obayashl and Jacobs, 1958; Westphal and Jacobs, 196I; Radoski and C a r o v i l l a n o , 1966). I t i s not u n t i l r e c e n t l y , however, that a t h e o r e t i c a l attempt has been made to study the p o l o i d a l o s c i l l a t i o n i n the magnetosphere. I t i s widely b e l i e v e d that the Pc3 range of p u l s a t i o n i s caused by a standing wave of modified 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 the plasmapause and the ionosphere. Experimental evidence based on observations made at a l o w - l a t i t u d e s t a t i o n by Hirasawa and Nagata (1966) and Nagata and Pukunishl (1968) provides support to 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 that the poloidal'wave equation i s separable in. s p h e r i c a l coordinates under the assumption of an axisymmetric plasma d e n s i t y ( i . e . the A l f v e n speed 8 i n c r e a s e s l i n e a r l y w i t h r a d i a l d i s t a n c e ) and ambient d i p o l e f i e l d . These s i m p l i f y i n g assumptions are c o n s i d e r e d t o r e p r e s e n t a r e a s o n a b l e f i r s t a p p r o x i m a t i o n a p p l i c a b l e i n the plasmasphere. R a d o s k i ' s c a l c u l a t i o n shows t h a t t h e z e r o o r d e r f u n damental p e r i o d of p o l o i d a l o s c i l l a t i o n i n the plasmasphere i s 34.2 seconds w i t h the second o r d e r c o r r e c t i o n l e s s t h a n one second, which i s the mean p e r i o d of Pc3 t y p i c a l of mid- 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 of m o d i f i e d A l f v e n mode has a l s o been c o n s i d e r e d t o e x i s t i n the pl a s m a t r o u g h . A s i m p l i f i e d 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 by T r u s s e l l (1966) s u g g e s t s t h i s p o s s i b i l i t y . Indeed, the r e s u l t of T r u s s e l l ' s c a l c u l a t i o n n o t o n l y i n d i c a t e s t h a t p e r i o d s o f the p o l o i d a l o s c i l l a t i o n i n the pl a s m a t r o u g h are i n the Pc3,4 range, i t a l s o p r e d i c t s a change o f thes e p e r i o d s as a f u n c t i o n o f the degree o f magnetospheric d i s t u r b a n c e r e p r e s e n t e d by the sum of Kp, i . e . ^ K p . T h i s has been summarized by a graph shown i n P i g . 1.3 which i s t o be compared w i 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 r e p o r t e d i n Chapter IV (see F i g . IV.2b). I t has been observed i n the p r e s e n t r e s e a r c h t h a t 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 s e t up i n b o t h the plasmasphere and the pla s m a t r o u g h i s assumed, some of the e x p e r i m e n t a l 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 R a l s t o n s t a t i o n may be e x p l a i n e d , namely, the apparent 9 d i v e r s i t y of 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 Pc3 from one day to a n o t h e r . 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 each of the 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 appear as a f u n c t i o n of the Kp i n d e x I s p r e s e n t e d i n the 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 by e x p e r i m e n t a l o b s e r v a t i o n as d i s c u s s e d i n Ch a p t e r 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 t h a t R a l s t o n , , 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 , 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 y o r i g i n a t i n g f r o m the plasmasphere and/or the p l a s m a t r o u g h depending upon the r e l a t i v e p o s i t i o n of the plasmapause. Two d i f f e r e n t approaches have been proposed 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 the pl a s m a t r o u g h and the plasma-sphere. I n the f i r s t approach, one may t a k e c o n t i n u o u s o b s e r v a t i o n s o ver a s i n g l e s t a t i o n i n the m i d - l a t i t u d e s . The movement o f the plasmapause w i l l be m a n i f e s t e d i n the chan g i n g d i m e n s i o n s of each o r b o t h of the e a r t h ' s two magnetic r e s o n a t o r s , which i n t u r n are r e p r e s e n t e d i n the ch a n g i n g e i g e n p e r i o d o f the ground-observed m i c r o p u l s a t i o n (Pc3 r a n g e ) . The movement of the plasmapause depends on the l e v e l of 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 the v a r i a t i o n of the s o l a r wind parameters r e p r e s e n t e d by the cha n g i n g v a l u e of the K^ i n d e x . At c e r t a i n l e v e l s of magnetic a c t i v i t y , r e p r e s e n t e d by d i f f e r e n t v a l u e s o f K , boundary e f f e c t s may be observed at R a l s t o n t h a t w i l l 10 i n d i c a t e the approximate l o c a t i o n of the plasmapause. The Kp dependence of Pc3 observed at Ralston w i l l be studied i n Chapter IV. The second approach one may take to l o c a t e the plasmapause i s to have simultaneous observations 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 along the same meridian. Comparison' of these simultaneous records would i n d i c a t e the l a t i t u d e dependence of Pc3 frequency which i n t u r n would provide 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 superior .to the f i r s t , provided 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 operating 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 to 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 given i n s t a n t of time. In Chapter V, the latitude-dependence as w e l l as the l o c a l time dependence of Pc3 are studied 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 guide-l i n e . A network of three 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 that two of them, namely Great Whale Riv e r and M c G i l l , l i e cl o s e to the same geomagnetic meridian whereas Ralston and M c G i l l are at about the same geomagnetic l a t i t u d e . The t e l l u r i c sonagrams published i n High L a t i t u d e Geophysical Data by the Geophysical I n s t i t u t e , C o l l e g e , Alaska over a period from. January to March 1967 have also been used f o r comparison. 1 1 The o b s e r v a t i o n a l r e s u l t s t h u s o b t a i n e d p r o v i d e f u r t h e r s u p p o r t f o r t h e p o s t u l a t e d m o d e l d e s c r i b e d i n t h e p r e v i o u s c h a p t e r s . A p r e l i m i n a r y s t u d y h a s b e e n c a r r i e d o u t on Pc4 o b s e r v e d a t R a l s t o n , t h e r e s u l t o f w h i c h w i l l be r e p o r t e d i n C h a p t e r V I . I n t h e f i n a l c h a p t e r , we s h a l l p r o p o s e f u t u r e e x p e r i m e n t s so t h a t some o f t h e i d e a s d e s c r i b e d i n t h i s t h e s i s may be i n v e s t i g a t e d . 12 FIG- 1.1 THE MAGNETOSPHERIC REGIONS 13 FIG. 1 . 2 MAQNETOSPHERIC EQUATORIAL ALFVEN VELOCITIES f m H z 70 60 50 40 30 20 10 0 5 10 15 20 25 30 35 50~ FIG. 1.3 THEORETICAL ESTIMATION OF DEPENDENCE 0F~PC 2, 3 and 4 PERIOD IN THE PLASMATROUGH ON MAGNETIC ACTIVITY (AFTER TRUSSEL,1966) 15 CHAPTER I I  SOURCE OF DATA AND INSTRUMENTATION I I . 1 SOURCE OF DATA Data r e c o r d e d on c h a r t s and r e c e n t l y a l s o on t a p e s have been made a v a i l a b l e t h r o u g h the Defence R e s e a r c h E s t a b -l i s h m e n t , P a c i f i c . F o r more t h a n e i g h t y e a r s c o o p e r a t i v e f i e l d work has been c a r r i e d out between the Radio S c i e n c e L a b o r a t o r y , S t a n f o r d U n i v e r s i t y , the P a c i f i c N a v a l L a b o r a t o r y (now the D.R.E.P.) and the U n i v e r s i t y of B r i t i s h C o lumbia. One of the main i n t e r e s t s has been c o n j u g a t e p o i n t s t u d i e s a t the two s t a t i o n s , G r e a t Whale R i v e r and B y r d . A t h i r d m i d - l a t i t u d e s t a t i o n a t R a l s t o n , A l b e r t a was a l s o e s t a b l i s h e d . A l l s t a t i o n s are i n s t a l l e d w i t h i d e n t i c a l systems. Magnetograms r e c o r d e d a t M c G i l l f o r s p e c i f i c days i n the e a r l i e r y e a r s (1963-1965) are a l s o a v a i l a b l e t h r o u g h the c o o p e r a t i o n of the D.R.E.P. 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 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 o ver a p e r i o d from J a n u a r y t o March 1967 has 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 . I n F i g . I I . l a , a map i s p r o v i d e d showing the r e l a t i v e p o s i t i o n of the v a r i o u s s t a t i o n s . The geomagnetic and ge 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 of each s t a t i o n are l i s t e d i n Table I I . 1 . 16 : ... The a v a i l a b l e data on the ra p i d v a r i a t i o n of the earth's magnetic f i e l d were recorded i n three orthogonal f i e l d components X, Y, and Z along the geographic east-west, north-south 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 to be made among s t a t i o n s , care must be taken to account f o r any l o c a l anomaly that may e x i s t . Weaver (1963) and others have shown that 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 to h o r i z o n t a l components of the magnetic f i e l d . However, since even dry ea r t h i s a good r e f l e c t o r as f a r as mic r o p u l s a t i o n frequencies are concerned the magnitude of the h o r i z o n t a l components should not be g r e a t l y a f f e c t e d by the nearness of 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 to w i t h i n at l e a s t a f a c t o r of two; see f o r example C h r i s t o f f e l et 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 of the h o r i z o n t a l components were only s l i g h t l y a f f e c t e d by the con t r a s t i n c o n d u c t i v i t y . Lokken (1964) a l s o found that 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 expected, are very much reduced i n i n t e n s i t y over Sable I s l a n d . Throughout the course of the study to be reported here t h e r e f o r e , only the h o r i z o n t a l X and Y components are used f o r i n v e s t i g a t i o n . No attempt has been made to deduce any conclusions that include the Z component. 17 A l s o , s i n c e the X and Y components a r e v e r y s i m i l a r , we have p r o c e s s e d from R a l s t o n a l l o f the 1967 magnetic tape d a t a f o r the X component whereas tape r e c o r d e d d a t a f o r 3 months o n l y ( F e b r u a r y , March, and August 1967) have been p r o c e s s e d f o r the Y component. Only the X component r e c o r d e d on tape i s o f s u f f i c i e n t l y low n o i s e t o s i g n a l r a t i o a t Great Whale i n the P c 2 , 3, and 4 f r e q u e n c y range, and d a t a f o r t h r e e months ( F e b r u a r y , March, and August 1967) have been p r o c e s s e d . 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 r e a v a i l a b l e from R a l s t o n , B y r d and Great Whale i n b o t h X and Y components. N o r m a l l y they 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 3/4 i n c h / m i n was used, 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 r e s o l u -t i o n . High-speed 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 from M c G i l l and Westham I s l a n d i n b o t h X and Y components f o r s p e c i f i c time i n t e r v a l s . Of the 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 v a i l a b l e , a s y n o p t i c e x a m i n a t i o n o n l y has been t a k e n . The d a t a a r e so s e l e c t e d t h a t o n l y those a v a i l a b l e s i m u l t a n e o u s l y from a maximum number o f s t a t i o n s a r e used. I n T a b l e II.2, the d i f f e r e n t forms o f 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 . The d e s i g n a t i o n s X, Y, and XY r e p r e s e n t the f i e l d components examined i n t h a t p a r t i c u l a r time i n t e r v a l . XY means X and Y. TABLE II.1 THE LOCATION AND MAGNETIC ELEMENTS OF STATIONS  FROM WHICH DATA WAS MADE AVAILABLE Geographic Geo magnet ic I n c l . of Average To t a l F i e l d Station — Left (N) Long (W) Lat (N) -Long (E) Field Line HJ_ _D_ ZJ_ Byrd (BY) -80°00' 119°30' -70°.6 336°.3 - 74°.8 15,330 68°28» 57,400 Great Whale n n River(GW) 55°l6' 77 47' 66 .6 347°.4 81°.1 9,450 21°39' 5^,700 College (Co) 64°'52' 147°50' 6 4 - 6 256°.5 7 7 ° . 0 12,610 -28°07* 55,227 Ralston 0 ^ (RA) 51 12' l l l o 0 7 , 53°.8 305 .5 72°.0 17,045 19 45' 52 , 466 Eights (EI) -75 34» 77 10' -63°.8 355°.3 -67°.1 22,500 32°00» 53,084 McGill (MG) 45°32' 7 3 o 0 9 , 57°.0 354 .3 74°.9 15,220 15°20» 56,170 Westham Island (WI) 49°06» 123°11» 54°.7 292°.9 71°.0 18., 860 22°.35' 53 , 2 05 20 TABLE I I . 2 SELECTED DATA USED ' IN THE PRESENT INVESTIGATION Form o f Data Date. GW S t BY a t RA i o n MG s WI E I 1967 Jan X s Feb X XY Mar X XY Apr' X Tape (FM) May- X 0.025 i n . / s e c June X J u l y X Aug X XY Sept X Oct X Nov X Dec X 1967 Feb 14-20 XY XY Aug 14-20 XY XY XY - 1966 Aug 15-20 XY XY XY Nov 16-18 Y Y Y to -p 3/4 i n / m i n 1965 Jun 14-25 XY XY XY S-i 03 x: Sep 14-25 XY XY XY XY F 0 Dec 15-22 XY XY XY XY w W 1964 J a n 15-20 Y Y Y Y < Apr 15-20 Y Y Y Y Y 0) c •r-i 1967 Jan XY XY H Feb 1-13 XY XY Este Feb 22-30 XY XY Este 6 i n / h o u r Mar Oct Nov Dec XY XY XY XY XY XY XY XY 21 Form o f Data Date GW S t BY a t i 0 n s RA MG WI E I .1967 J a n Y Y Y Feb Y . Y Y Mar Y Y Apr Y H e l i c o r d e r May Y C h a r t June Y 3 cm/min J u l y Y Aug Y Y Sept Y Oct Y Nov • Y Dec Y La Cour Type. Magnetogram 2 cm/min 1965 Jun 14-Sep 14-Dec 15-25 25 22 HD HD HD 22 I I . 2 RECORDING AND REPRODUCING SYSTEM The r a p i d v a r i a t i o n of the geomagnetic f i e l d has been resolved i n t o three orthogonal components f o r the purpose of d e t e c t i o n . The d e t e c t i n g equipment i n the h o r i z o n t a l axes (X i n the geographic north-south and Y i n the east-west d i r e c t i o n s ) c o n s i s t e d of mumetal cored s o l e n o i d s . S i g n a l s received by these c o i l s were fed to recorders through d.c. chopper a m p l i f i e r s . Two types of data recorders were used. One i s the E s t e r l i n e Angus chart recorder, with a chart speed of 6 i n c h per hour or with a higher speed of 3 / 4 i n c h per minute. For a n a l y s i s , the higher 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 the slower speed f o r P c 3 , 4 and 5 s i g n a l s . The higher speed was required to resolve P c 2 while the long period P c 5 could best be observed at the slower speeds. Data may al s o be recorded on magnetic tapes. The recor d i n g tape speed i s 0 . 0 2 5 i n c h per second ( 7 - 5 f t . per hour). This provide 10 days of continuous 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).' In order to i d e n t i f y events recorded on tapes, simultaneous recordings were made on h e l i c o r d e r c h a r t s operating with a chart speed of 3 cm per min. The frequency domain of i n t e r e s t defined by the D.R.E.P. group ( E n g l i s h et a l , 1 9 6 l ) who were responsible f o r the experimental operations, has an upper frequency 23 l i m i t of 100 Hz and a lower l i m i t of 0.01 Hz. The frequency-response c u r v e f o r the equipment o f the D.R.E.P. group, g i v e n by E n g l i s h e t a l (1961), 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 r e c o r d i n g system i s shown i n P i g . I I . 2 b , a d e t a i l e d d e s c r i p t i o n of which may be found i n the T e c h n i c a l Memoranda p u b l i s h e d by the Defence R e s e a r c h Board o f Canada ( w e i r , 1966; Lokken 1964; Shand e t a l , 1959; Gibb, 1968). The r e p r o d u c t i o n speed f o r the tape i s 3-3/4 i n c h per second, g i v i n g a f r e q u e n c y m u l t i p l i c a t i o n of 150, t h e r e f o r e 10 days of d a t a can be p l a y e d back i n 1.6 h o u r s . The r e c o r d bandwidth i s 0 t o 4.0 Hz and the r e p r o d u c t i o n bandwidth i s 0 t o 600 Hz. s o D E T E C T O R N O . I S F I L T E R 'fit A J A P U F I E . R M O . I-WLS F O R T C H U R C H U _ V _ , | V \ A N . O C T . 2 . , 1^60 O O l O ' l Fceouervcy PIG. II.2a l - O Cycles per second FREQUENCY RESPONSE OF F. M. RECORDING oYSTEM IO Monitor Calibration -i \A/V r-I Current I o u 1 a> ; o Input Filter X 7 ^ Signal Generator Chopper Amplifier Input Fi lter Slow Speed F. M. Record 1 U n i 1 X 2 Y 3. Z 4 Single Channel Reproduce Monitor Unit £ 9-3 > 6 6 I 6 4 4 S l o w Sp Tape T r o c k 1 2 » 3 " 4 FIG. I I . 2 b MICROPULSATION RECORDING SYSTEM 26 I I . 3 TAPE ANALYSING SYSTEM I n o r d e r t o f e e d t h e ou t p u t o f t h e r e p r o d u c i n g u n i t (which has a l r e a d y been m u l t i p l i e d by 150 t i m e s the f r e q u e n c y 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, the o u t p u t s i g n a l must be f u r t h e r speeded t o s u i t t h e d e s i g n o f t h e sonagraph. To a c h i e v e t h i s , the output of 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 Sanborn tape r e c o r d e r w i t h a r e c o r d i n g speed o f 15/16 i n c h p e r second ( r e c o r d i n g bandwidth i s d.c. t o 313 H z ) . The r e c o r d e d s i g n a l i s t h e n p l a y e d back w i t h a h i g h e r speed o f 60 i n c h p e r second ( r e p r o d u c e bandwidth i s d.c. t o 20 KHz), t h u s a r e s u l t a n t speed-up f a c t o r o f 150 x 64, or 96OO, has been a c h i e v e d . Thus, a m i c r o p u l s a t i o n s i g n a l i n the 0.01 t o 0.1 Hz. f r e q u e n c y range has now been speeded up t o 96 t o 96O Hz, ready t o be p r o c e s s e d by the sonagraph. 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 the Kay E l e c t r i c sonagraph are t a b u l a t e d i n Appendix 2 f o r r e f e r e n c e . The v i s u a l r e c o r d s which c o n t a i n t h e a n a l y s i s of the r e c o r d e d m i c r o p u l s a t i o n waves are made on n o n - p h o t o g r a p h i c , c u r r e n t s e n s i t i v e , f a c s i m i l e - t y p e paper. The paper i s mounted on a drum whose a x i s i s t h e same as the t u r n t a b l e on whose p e r i p h e r y the c o n t i n u o u s magnetic r e c o r d i n g f i l m i s d e p o s i t e d . The arrangement p r o v i d e s a u t o m a t i c time s y n c h r o n i z a t i o n . The r e c o r d i s t r a c e d by a s t y l u s which advances upward, and a t the same time changes the apparent c e n t e r f r e q u e n c y of the 2 7 a n a l y z i n g band pass f i l t e r . A high-frequency current a p p l i e d to the s t y l u s i s v a r i e d i n amplitude i n p r o p o r t i o n to the amount of energy passed by the bandpass f i l t e r . The f i r s t type of record obtainable d i s p l a y s time on the ab s c i s s a , frequency on the ord i n a t e , and i n t e n s i t y as shading between gray and black. The second type of record d i s p l a y s i n t e n s i t y i n db vs. frequency at as many as s i x s e l e c t e d times. 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 record d i s p l a y s average a v a i l a b l e amplitude vs. time w i t h i n a dynamic range of 3^ db maximum. Only the f i r s t type of record, i . e . the frequency-time d i s p l a y , however, has been found u s e f u l i n our present i n v e s t i g a t i o n . In a d d i t i o n , a Kay E l e c t r i c contour u n i t has been used to produce contoured sonagrams which are u s e f u l i n l o c a t i n g the mid-band frequency of a given s i g n a l . A scale expander i s a l s o a v a i l a b l e to expand the frequency scale so t h a t , coupled with a c o r r e c t choice of recording speed, any p o r t i o n of a given spectrogram may be expanded to show a f i n e r d e t a i l . The t e l l u r i c sonagrams published i n High L a t i t u d e Geophysical Data by the Geophysical I n s t i t u t e , C ollege, Alaska 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 period range of 9 to 500 sec. The t e l l u r i c system has the advantage of l a r g e r low frequency response 28 than an i n d u c t i o n l o o p system and a b e t t e r s i g n a l t o n o i s e r a t i o because of the m i l l i v o l t s a v a i l a b l e f r om t h e t e l l u r i c 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 s i g n a l of the i n d u c t i o n l o o p . The a m p l i f i e r i s a M e d i s t o r m i c r o v o l t m e t e r s e t a t 10 mv range and l o g a r i t h m i c s c a l e . The l o g a r i t h m i c response makes i t p o s s i b l e t o accommodate the wide dynamic range of a c t i v i t y 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 under i n v e s t i g a t i o n . 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 low a m p l i t u d e Pc3 daytime a c t i v i t y can be brought out c l e a r l y on the sonagrams, and w i t h no o v e r l o a d i n g of the i n s t r u m e n -t a t i o n due t o the p o w e r f u l n i g h t t i m e P i a c t i v i t y . The tape r e c o r d e r i s a K n i g h t 4000A d i r e c t r e c o r d i n s t r u m e n t which has been m o d i f i e d to r e c o r d a t 1-1/6 i n c h per hour. The f r e q u e n c y response of the 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 are shaped such t h a t average a c t i v i t y a t the bottom o f sonagram i s not too b l a c k and average a c t i v i t y a t the top i s not too f a i n t . To a c c o m p l i s h t h i s , the response 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 toward h i g h e r f r e q u e n c i e s . I f a f l a t response had been used, the upper p a r t o f the sonagrams would 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 l e v e l was p r e s e n t a t the bottom. The d e p a r t u r e from f l a t n e s s i s not s u f f i c i e n t t o s i g n i f i c a n t l y d i s t o r t the Pc3-5 a c t i v i t y . 29 CHAPTER I I I SUBCLASSIFICATION OF Pc3 IN MID-LATITUDE-DIURNAL  VARIATION OF Pc3 FREQUENCY AT RALSTON I I I . l INTRODUCTION R e c e n t l y , v a r i o u s a u t h o r s have shown from s a t e l l i t e d a t a t h a t t h e r e i s a d e f i n i t e c o n n e c t i o n between the p e r i o d o f c o n t i n u o u s p u l s a t i o n (Pc 2, 3, and 4) and t h e changes of 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 T r o i t s k a y a , 1964; B o l s h a k o v a , 1965a; Nagata e t a l , 1 9 6 6 ) . The 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 o f c o n t i n u -ous p u l s a t i o n s may be a b l e to s e r v e as a new c h a r a c t e r i s t i c o f the s o l a r wind ( B o l s h a k o v a , 1965a; Nagata e t a l , 1966; T r o i t s k a y a , 1967). S i n c e a Pc3 event t a k e s p l a c e e v e r y day, i f the p e r i o d o f a Pc3 m i c r o p u l s a t i o n i s i n d e e d a m a n i f e s t a -t i o n o f the g e n e r a l p h y s i c a l c o n d i t i o n o f the magnetosphere and beyond, m i c r o p u l s a t i o n r e s e a r c h c o u l d p r o v i d e us c o n t i n u -o u s l y w i t h a most economic 'window' t o the 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 o f the c o n t i n u o u s 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 which i s n e a r l y as o l d as the s u b j e c t i t s e l f . E.R.R. Holmberg (1951, 1953) n o t i c e d the s y s t e m a t i c change o f Pc3 and Pc4 p e r i o d s and produced the w e l l -known s c a t t e r diagram of p e r i o d a g a i n s t time u s i n g d a t a o b t a i n e d by an i n d u c t i o n l o o p a t E s k d a l e m u i r as e a r l y as 1926 and 1927. S i n c e t h e n many workers have r e p o r t e d r e s u l t s o f t h e i r 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 s u b j e c t remains a m a t t e r of c o n t r o v e r s y even to d a y . Many a u t h o r s c o n c l u d e d from s c a l i n g magnetograms t h a t the f r e q u e n c y o f Pc3 behaves as a U-type ( 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 v a r i a t i o n (Kato and S a i t o , 1959; Y a n a g i h a r a , 1959; Pope e t a l , 1962; Holmberg, 1953), t h a t i s t o say the f r e q u e n c y o f Pc3 i s lo w e r i n the a f t e r n o o n t h a n 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 by 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 r e c o r d e d on c h a r t s as w e l l as on slow speed magnetic t a p e s demonstrates the c o n t r a r y . U s i n g slow speed magnetic tape d a t a r e c o r d e d at K a k i o k a F i e l d S t a t i o n i n Japan (26.0° i n geomagnetic l a t i t u d e ) , Hirasawa and Nagata (1966) r e p o r t e d t h a t the f r e q u e n c y of P c 3 appears t o be h i g h e r e a r l y i n the morning and t h e n d e c r e a s e s t o t h e l o w e s t p o i n t l a t e i n the a f t e r n o o n . T h i s r e p o r t agrees w i t h the r e s u l t shown e a r l i e r by Duncan (1961) u s i n g a l s o slow speed tape r e c o r d e d d a t a and c h a r t s from Hobart ( (p = 5 2 ° ) , Camden ( 6 = 43°), A d e l a i d e ( 6 = 45°) and T o w n s v i l l e ( 0 = 2 9 ° ) i n A u s t r a l i a . Other a u t h o r s , n o t i c e a b l y S t u a r t and Usher (1966) observed a s i m i l a r t r e n d a t L e r w i c k ( <ji = 62.6°), but d i f f e r e n t a t E s k d a l e m u i r { (j) = 5 8 . 5 ° ) and H a r t l a n d ( $ = 55.1°). At E s k d a l e m u i r , 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 s v e r y s l i g h t whereas an 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 i n f r e q u e n c y i s apparent at H a r t l a n d . Nagata and F u k u n i s h i (1968) a l s o found 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 f r e q u e n c y a t K a k i o k a , Japan. 31 Each o f the above mentioned t y p e s o f 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 has been i d e n t i f i e d a t R a l s t o n ( C) = 58.8°). 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 . The U-type i s found t o be the l e a s t f r e q u e n t . Out o f the d a t a under s t u d y i n 1967 o n l y two such cases were found, and t h e s e o c c u r r e d o n l y under i r r e g u l a r magnetospheric c o n d i t i o n s . The U-type may t h e r e f o r e be t a k e n as an e x c e p t i o n a l case r a t h e r than a p e r s i s t e n t phenomenon. On t h e o t h e r hand numerous examples were found h a v i n g d i u r n a l 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 and Nagata, Duncan, S t u a r t and Usher, and Nagata and F u k u n i s h i . F u r t h e r m o r e , the 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 to 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 a r e about to propose i n t h i s c h a p t e r . S c r u t i n y o f d i s p l a y s o f sonagrams (dynamic s p e c t r a ) p r o c e s s e d from slow speed r e c o r d e d d a t a r e c o r d e d a t R a l s t o n s u g g e s t s t h a t t h e r e a r e f o u r b a s i c t y p e s 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 apparent under s t e a d y magnetospheric c o n d i t i o n s . The m a j o r i t y o f e v e n t s under 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 , o r the c o m b i n a t i o n o f , t h e s e f o u r b a s i c t y p e s . T h i s , however, does not Imply t h a t e x c e p t i o n s may not t a k e p l a c e , but the e x c e p t i o n w i l l r a r e l y o c c u r . Moreover, th e s e e x c e p t i o n s may be shown to t a k e p l a c e o n l y under r a p i d l y c h a n g i n g magnetospheric c o n d i t i o n s r e p r e s e n t e d by the i n d e x . An i n v e r s e r e l a t i o n between K and the r a d i u s o f the 32 magnetosphere was documented by C a h i l l and Amazeen (I963). Some of the e x c e p t i o n a l c a s e s w i l l be p r e s e n t e d i n S e c t i o n I I I . 6 . I n the f o l l o w i n g s e c t i o n s t h e f o u r proposed s u b - c a t e g o r i e s o f Pc3 c o n t i n u o u s p u l s a t i o n w i l l be d e s c r i b e d 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 . I I I . 2 MULTI-BAND STRUCTURED CONTINUOUS PULSATION One o f t h e most i n t e r e s t i n g f i n d i n g s t h a t j u s t i f i e s o u r p r o p o s a l f o r r e c l a s s i f i c a t i o n o r s u b c l a s s i f i c a t i o n o f c o n t i n u o u s p u l s a t i o n i s t h e e x i s t e n c e o f m u l t i - b a n d s t r u c t u r e i n f r e q u e n c y . E x p e r i m e n t a l e v i d e n c e i n d i c a t e s t h a t two o r t h r e e f r e q u e n c y b a n d s may o f t e n be i d e n t i f i e d w i t h i n t h e f r a m e w o r k o f B e r k e l e y r e s o l u t i o n ( J a c o b s e t a l , 1964) d e f i n i n g t h e b o u n d a r y ' o f Pc3 m i c r o p u l s a t i o n ( M a i n s t o n e , 1967). O c c u r r e n c e o f t h e s e d i s t i n c t Pc3 f r e q u e n c y s u b - b a n d s may n o t be u n u s u a l a t R a l s t o n . R a t h e r t h e y u s u a l l y o c c u r o n l y f o r a b r i e f i n t e r v a l o f t i m e . Or, when t h e f r e q u e n c y b a n d s o v e r l a p , t h e o r d i n a r y s o n a g r a p h f a i l s t o p r o v i d e s u f f i c i e n t r e s o l u t i o n t o r e v e a l them. I t h a s b e e n e v i d e n t t o u s f o r • some t i m e t h a t s c r u t i n y o f r a p i d - r u n m a g n e t o g r a m s (3/4 i n c h p e r m i n u t e c h a r t s p e e d ) o b t a i n e d a t m i d - l a t i t u d e s t a t i o n s may o f t e n i d e n t i f y d o u b l e p e r i o d i c i t y . F u r t h e r , t h e p e r i o d s o f t h e two waves s u p e r i m p o s i n g e a c h o t h e r a r e w i t h i n t h e Pc3 f r e q u e n c y r a n g e ( s e e F i g . I I I . 2 a ) . B u t a n a l y s i s b y s c a l i n g m a gnetograms h a s o f t e n p r o v e d t o be m i s l e a d i n g . No d e f i n i t e c o n c l u s i o n s may be d r a w n u n t i l f u r t h e r e v i d e n c e becomes a v a i l a b l e . I t i s r a t h e r f o r t u n a t e t h a t a s ample o f 13 d a y s I n t o t a l o f m u l t i - b a n d s t r u c t u r e d Pc3 h a s b e e n i d e n t i f i e d o u t o f t h e s l o w s p e e d t a p e r e c o r d e d d a t a o b t a i n e d a t R a l s t o n i n 1967. E a c h o f t h e s e m u l t i - b a n d s t r u c t u r e d Pc3 e v e n t s i d e n t i f i e d l a s t f o r a t l e a s t t h r e e hour.s. 3 4 I n T a b l e I I I . l , we have 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 Pc3 a t R a l s t o n i n 1967. We have l i s t e d a l s o t h e m i d - f r e q u e n c y o f each band f o r comparison. With an o n l y e x c e p t i o n o f f ^ which i s i n the Pc4 range, the o t h e r t h r e e bands f 2 , and f 4 a r e i n s i d e the boundary o f Pc3 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 . I n o r d e r t o l o c a t e the m i d - f r e q u e n c y o f each i n d i v i d u a l sub-band a c c u r a t e l y , c o n t o u r e d sonagrams a r e made which have been found t o be most e f f i c i e n t . We have 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 which m u l t i - b a n d s t r u c t u r e has been obse r v e d on each o f t h e s e days. I t i s e v i d e n t from T a b l e I I I . l t h a t the m u l t i - b a n d 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. Onl y on the days o f m o d e r a t e l y d i s t u r b e d magnetic c o n d i t i o n s do we 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 morning ( n o t i c e a b l y on November 24, December 6, 1, and 8, 1967), and i t 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 days t h a t the f o u r t h band fjj. becomes n o t i c e a b l e . The a s s o c i a t i o n o f Pc4 w i t h the o c c u r r e n c e o f m u l t i -band Pc3 s h o u l d not be t a k e n as p u r e l y I n c i d e n t a l . F u r t h e r d i s c u s s i o n w i l l be g i v e n i n t h e l a t e r s e c t i o n s . I n F i g . I I I . 2 b one o f the most d e m o n s t r a t i v e examples o f m u l t i - b a n d s t r u c t u r e d Pc3 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 the day. The f r e q u e n c y o f a l l bands d e c r e a s e s as the day p r o c e e d s towards the a f t e r n o o n . There I s an enhancement o f Pc3 a c t i v i t y o b s e r v e d a t 1100 L.T. The enhancement o f b o t h Pc3 bands 35 TABLE I I I . l CHARACTERISTICS OF CLEAR MULTI-BAND CONTINUOUS PULSATION AT RALSTON IN 196? Date Mid f]_ Mid f„ Mid f 0 Mid f,j Time of Occurrence Maximum I n t e n s i t y Feb '5 22 0 . 0 1 0 0 . 0 2 5 0.040 O .065? 10 - 12 LT 11 - 12 LT Feb 11 19 0 . 0 1 0 0 . 0 2 2 0.038 -- Daytime Noon Feb 12 4 0 . 0 1 0 0 . 0 2 2 0 . 0 3 5 — 8 - 16 LT Noon Mar 3 15 0 . 0 1 0 0 . 0 2 0 0 . 0 3 0 -- Daytime 15 - 16 LT J u l 12 17 0.012 0 . 0 2 5 0 . 0 3 5 — > 10 - 16 LT 13 LT Aug 23 10 o.olo 0 . 0 2 5 0.040 Daytime 12 - 14 LT Sep 3 12 0.012 0 . 0 2 5 0.040 -- Daytime 15 - 18 LT Sep 4 13 0.012 0 . 0 2 5 0 . 0 3 5 — 4 - 21 LT 16 - 19 LT Oct 13 17 0 . 0 1 0 0 . 0 2 5 O.O38 Daytime 11 - 16 LT Oct 23 15 0 . 0 0 8 0 . 0 2 0 0 . 0 3 0 — Daytime 12 - 14 LT Nov 16 17 0 . 0 1 5 0 . 0 2 5 O.O38 O.OoO 5 - 18 LT 9 13 LT Nov 23 16 0 . 0 1 0 0 . 0 2 8 0.045 0 . 0 7 0 ? Daytime 13 - 15 LT Nov 24 27 0 . 0 1 0 0.025 0.040 0 . 0 7 0 5 - 17 LT 9 - 11 LT Dec 4 14 0.010 0 . 0 2 2 O.O38 — 6 - 21 LT 12 - 14 LT Dec 6 23 0 . 0 1 5 0 . 0 3 0 0.045 0 . 0 7 0 5 - 19 LT 10 - 17 LT Dec 7 27 0 . 0 1 0 0 . 0 2 8 0.042 0 . 0 6 5 6 - 18 LT 9 - 15 LT Dec 8 31 0 . 0 1 0 0 . 0 2 5 0.040 0 . 0 7 0 4 - 16 LT 7 -13 -8 14 LT LT Dec 12 12 0 . 0 0 8 0 . 0 2 0 0 . 0 3 5 -- 8 - 18 LT 17 - 18 LT Average 0 . 0 1 1 0.024 O.O38 36 t a k e s p l a c e s i m u l t a n e o u s l y . T h i s i s d i f f e r e n t f r om the Pc4 band whose i n t e n s i t y has been enhanced e a r l i e r i n the morning. Maximum i n t e n s i t y t a k e s p l a c e around noon f o r a l l t h r e e 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 o c c u r r i n g j u s t b e f o r e and a f t e r the l o c a l m i d n i g h t . The m a j o r i t y of m u l t i - b a n d e v e n t s are o b s e r v e d around noon o r e a r l y i n the a f t e r n o o n . The f r e q u e n c y o f t h e s e t y p e s o f Pc3 i s e i t h e r c o n s t a n t o r d e c r e a s i n g . T h i s i s d i f f e r e n t from the t y p e s t h a t are observed i n the. morning. The morning type o c c u r s o n l y r a r e l y , and t h o s e o b s e r v e d d i s p l a y an i n c r e a s i n g f r e q u e n c y t r e n d toward noon. Two examples, shown i n F i g . I I I . 2 c and F i g . I I I . 2 d , i l l u s t r a t e the case o f m u l t i -band Pc3 w i t h c o n s t a n t f r e q u e n c y o c c u r r i n g i n the a f t e r n o o n , and the case o f m u l t i - b a n d Pc3 w i t h i n c r e a s i n g f r e q u e n c y o c c u r r i n g i n the morning. I n F i g . I I I . 2 e , one example of d i s t i n c t 4 band s t r u c t u r e has been demonstrated. T h i s o c c u r s on a day when the g e n e r a l d i s t u r b a n c e l e v e l i s h i g h . But t h e magnetic a c t i v i t y t a k e s p l a c e f a i r l y s t e a d i l y as i n d i c a t e d by the s t e a d y v a l u e o f the Kp i n d e x . I t i s i n t e r e s t i n g t o note the s p i k e - l i k e d i s c r e t e appearance of the s p e c t r o g r a m which i s most apparent a f t e r 1500 L.T. T h i s i s c o n t r a r y t o t h e g e n e r a l l y c o n t i n u o u s and d i f f u s e d appearance, such as o c c u r r e d on F e b r u a r y 12, 1967, F i g . I I I . 2 c . J 1 1 L I l I I I I i 1950 1955 u. FIG III2a September 18.1965 M U L T I - P E R I O D I C I T Y O F Pc3 38 U.T. L.T. 23 1 6 8 10 12 14 16 18 20 22 i I i I • I • 2 4 6 7 9 11 13 15 17 19 21 23 TVI»E e «S S O N A G R A M & KAY ELBCTIUC CO. PINE BROOK. N. J. 6 0 -40-20-FIG lll.2b RALSTON Y 11 FEB 67 .MULTI-BAND Pc3 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 IN THE EARLY MORNING 41 FIG lll.2e RALSTON X 6 DEC 67 4 BANDS STRUCTURED Pc3,4 42 I I I . 3 NORMAL TYPE WITH MORNING AND AFTERNOON SEPARATION Ve r y o f t e n , Pc3 o b s e r v e d i n the morning behaves d i f f e r e n t l y from t h a t o b s e r v e d i n the a f t e r n o o n o r i n the ev e n i n g . The morning type Pc3 i s u s u a l l y o f l o w e r f r e q u e n c y than i t s c o u n t e r p a r t i n the a f t e r n o o n . The morning type Pc3 behaves as an i n v e r t e d U-type d a i l y 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. T h i s t r a i n u s u a l l y b e g i n s around 0200 o r 0300 L.T. w i t h low f r e q u e n c y which would t h e n I n c r e a s e towards dawn. A f t e r g o i n g t h r o u g h the maximum f r e q u e n c y n e a r dawn, the f r e q u e n c y b e g i n s t o t a k e a downward t r e n d u n t i l I t re a c h e s the l o w e s t p o i n t e a r l y i n the a f t e r -noon. Towards 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 the 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 the a f t e r n o o n and then i t s f r e q u e n c y d i m i n i -shes r a p i d l y toward dusk (lbOO L . T . ) . T h i s I s demonstrated p r o f o u n d l y by an example shown I n F i g . I I I . 3 a . The boundary between the morning and the 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 the boundary i s d i f f i c u l t t o l o c a t e . T h i s happens when the two bands o v e r l a p each o t h e r a t the boundary. There i s s t r o n g Kp dependence on the o c c u r r e n c e time of the boundary between the morning and the a f t e r n o o n type 43 Pc3. Under moderately d i s t u r b e d c o n d i t i o n s corresponding to Kp = 3 — * 4 , the boundary e f f e c t takes place e a r l i e r i n the morning. On the other hand, when the magnetic c o n d i t i o n i s reasonably quiet ( 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 the a f t e r -noon type of Pc3 begins i n the morning. This occurs when the l e v e l of magnetic disturbance i s reasonably high ( ^ Kp> 25 say).. I t s frequency then decreases as the day proceeds towards the afternoon. The morning type of Pc3 i s only vaguely recognizable, and the separation between the morning type Pc3 and Pc4 i s not too c l e a r . I t i s t h i s type of d i u r n a l v a r i a t i o n of frequency that Hlrasawa and Nagata (1966) reported from Kakioka, Japan (see P i g . I I I . l ) . Because the morning type of Pc3 observed at high and m i d - l a t i t u d e s become very weak at the lower l a t i t u d e , observers at low-l a t i t u d e s t a t i o n s would tend to average out the d i f f e r e n c e between t h i s type of Pc3 with the much stronger s i g n a l of Pc4. Vie s h a l l leave f u r t h e r d i s c u s s i o n of t h i s t o p i c to the l a t e r chapter on'the comparative study of continuous p u l s a t i o n s at 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 l o n g i t u d e s . The example given i n P i g . I I I . 3 c i s a t y p i c a l observation at Ralston under quiet magnetic c o n d i t i o n s ( £K = 3 i n t h i s c ase.). As shown i n the spectrogram, P c 3 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 with 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 . At 1530 L. the boundary between the morning and a f t e r n o o n type o f Fc3 m a y be i d e n t i f i e d . Soon a f t e r 1600 L.T. the second t r a i n of h i g h e r f r e q u e n c y t a k e s o v e r . There i s some o v e r l a p p i n g of f r e q u e n c y between the two t r a i n s as i s c l e a r l y shown i n the c o n t o u r e d sonagram i n the l o w e r p o r t i o n of P i g . I I I . 3 c Pc'l i s observed o n l y r a r e l y a t R a l s t o n under v e r y q u i e t and s t e a d y magnetic c o n d i t i o n s . The p a r t i c u l a r case where we do not observe Pc3 i n the morning may o c c a s i o n a l l y t a k e p l a c e at R a l s t o n . An example g i v e n 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 f e a t u r e s r e p o r t e d by Hirasawa and Nagata. The o c c u r r e n c e of t h i s type i s v e r y r a r e at R a l s t o n . I t o c c u r s o n l y when the magnetosphere i s .expanding r a p i d l y (see the Appendix 1 f o r the t a b l e of K D i n d e x ) . There i s another f e a t u r e which i s v e r y i n t e r e s t i n g and common t o most spectrograms observed at R a l s t o n . I t has been n o t i c e d t h a t even f o r the most c o n t i n u o u s e v e n t s o b s e r v e d , a ' b l a n k 1 o f 20 t o 60 minute i n t e r v a l may o f t e n take p l a c e . T h i s 'pause' of m i c r o p u l s a t l o n a c t i v i t y t a k e s p l a c e a b r u p t l y , and i t does not a f f e c t the c o n t i n u i t y of the p u l s a t i o n event i n o t h e r time i n t e r v a l s . Under m i l d l y d i s t u r b e d c o n d i t i o n s t h i s abrupt pause of a c t i v i t y u s u a l l y o c c u r r e d e a r l y i n the a f t e r n o o n , but t h e r e are ca s e s where the pause i s found e a r l i e r i n the morning. 45 I n P i g . I I I . 3 b , the pause was a t 1230 L.T. and l a s t e d f o r about h a l f an hour. The pause o f the F e b r u a r y 10 event o c c u r r e d at 1345 L.T. and l a s t e d o n l y about t e n minutes (see P i g . I I I . 3 c ) . The March 19 event shown i n F i g . I I I . 3 e t o o k p l a c e under d i s t u r b e d c o n d i t i o n s (^K = 29). The pause of t h i s P p a r t i c u l a r event o c c u r r e d i n the morning. I t i s noted t h a t i n a l l the c a s e s shown, the pause t o o k p l a c e o n l y i n the Pc3 f r e q u e n c y range. The Pc4 i n b o t h examples shown i n F i g . I I I . 3 b and F i g . I I I . 3 © are not a f f e c t e d . TVPt B, BS SON A a RAM • KAY ELECTRIC CO. PINE BROOK. N. J. - « U.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 L.T. 23 1 3 5 7 9 11 13 15 17 19 21 23 T I M B aa (ONAOffAM • KAY KLECIRJC CO. PINK BROOK. M. X FIG lll.3a RALSTON X 18 OCT67 NORMAL TYPE WITH MORNING AND AFTERNOON SEPARATION 4 7 FIG III.3b RALSTON X 7 DEC 67 NORMAL TYPE UNDER DISTURBED CONDITIONS 4 8 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 MAR 19,67 THE 'PAUSE' THAT OBSERVED IN THE MORNING 51 111.4 THE INVERTED U-TYPE V/ITH DISCRETE STRUCTURE V e r y o f t e n , Pc3 o b s e r v e d a t R a l s t o n , u n d e r m o d e r a t e l y q u i e t c o n d i t i o n s (Kp<;2) b e h a v e s 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 f r e q u e n c y . F u r t h e r , u n l i k e a n y t h i n g t h a t h a s b e e n so f a r r e p o r t e d b y o t h e r w o r k e r s , t h e d y n a m i c s p e c t r u m o f Pc3 may o f t e n t a k e a s p i k e - l i k e d i s c r e t e a p p e a r a n c e . The t i m e i n t e r v a l b e t w e e n s u c c e s s i v e s p i k e s i s u s u a l l y a b o u t h a l f t o one h o u r a l t h o u g h t h e y do n o t o c c u r a t r e g u l a r t i m e i n t e r v a l s . The w i d t h o f e a c h s p i k e i s o f t h e o r d e r o f t e n t o t w e n t y m i n u t e s . The s p i k e o f maximum f r e q u e n c y a p p e a r s a r o u n d l o c a l n o o n , b u t no d e f i n i t e r u l e h a s b e e n o b s e r v e d g o v e r n i n g t h e o c c u r r e n c e o f s u c h s p i k e s . Two e x a m p l e s a r e g i v e n i n F i g . I I I . 4 a and F i g . I I I . 4 b . B o t h e v e n t s shown o c c u r u n d e r q u i e t b u t n o t t o o s t e a d y m a g n e t i c c o n d i t i o n s i n d i c a t e d b y t h e l o w b u t f l u c t u a t i n g v a l u e s o f t h e Kp i n d e x . The s p i k e - l i k e s t r u c t u r e d Pc3 i s n o t r e s t r i c t e d t o t h e i n v e r t e d U - t y p e o f d i u r n a l b e h a v i o u r . A l l t h e o t h e r t y p e s m e n t i o n e d i n t h e p r e v i o u s t h r e e s e c t i o n s may a l s o t a k e a d i s c r e t e a p p e a r a n c e . We p r e f e r t o c o n s i d e r them as a m i x t u r e o f t h e t y p e m e n t i o n e d i n t h i s s e c t i o n and t h e i r own t y p e . We a r e w e l l aware t h a t t h i s c l a s s i f i c a t i o n i s n o t u n i q u e . O n l y when t h e p h y s i c a l n a t u r e o f t h e s e s p i k e s becomes b e t t e r u n d e r s t o o d c a n one c l a s s i f y them i n a s t r i c t manner. 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 I I I . 5 THE DIFFUSED INVERTED U-TYPE There i s an o t h e r type o f Pc3 a c t i v i t y o b s e r v e d a t R a l s t o n which a l s o d i s p l a y s an i n v e r t e d U-form of d a i l y v a r i a t i o n i n f r e q u e n c y . A sonagram of t h i s type 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 any p a r t i c u l a r time i n t e r v a l . We t h e r e f o r e c a l l e d t h i s type of a c t i v i t y a ' d i f f u s e d ' i n v e r t e d U-type i n c o n t r a s t t o the ' d i s c r e t e ' i n v e r t e d U-type d e s c r i b e d i n the l a s t s e c t i o n . The 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 s t e a d y and r e a s o n a b l y q u i e t magnetic c o n d i t i o n s . The word 'steady' s h o u l d be emphasized, because i t i s o n l y when t h e v a l u e of the i n d e x does n ot f l u c t u a t e o v er a c e r t a i n l e v e l f r om the mean v a l u e t h a t we may observe the d i f f u s e d i n v e r t e d U-type, whereas the d i s c r e t e 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 the magnetic c o n d i t i o n i s r e a s o n a b l y f l u c t u a t i n g . Of c o u r s e , one may a l s o t h i n k of t h i s d i f f u s e d t y pe as o n l y a p a r t i c u l a r case o f the d i s c r e t e t y pe w i t h the s p i k e s crowded t o g e t h e r . I n T a b l e I I I . 2 , 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 i n v e r t e d U-type Pc3. A l l the e v e n t s l i s t e d i n Table I I I . 2 have ZKp l e s s t h a n 15 because we have not been a b l e t o f i n d any good example of t h i s type where the v a l u e o f £Kp i s g r e a t e r . The average f r e q u e n c y o f e v e n t s 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 the most p r o b a b l e time 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 c a s e s under s t u d y have maximum f r e q u e n c y o c c u r r i n g one hour b e f o r e o r a f t e r 1300 L.T. TABLE I I I . 2 DATES OP DIFFUSED INVERTED U-TYPE  DIURNAL VARIATION OF FREQUENCY Date F mHz L.T. max f Nov 17, 1967 3_ 30 1200 Nov 18, 1967 5_ .29 1200 Oct 20, 1967 6_ 29 1330 Nov 19, 1967 6+ 30 1430 Mar 17, 1967 30 1230 Oct 16, 1967 30 1230 Aug 22, 1967 l l _ 25 1330 Mar 28, 1967 ^ 6 35 1400 Two examples of the D.I.U. type of d i u r n a l v a r i a t i o n are shown i n P i g . I I I . 5 a and F i g . I I I . 5 b where the i n v e r t e d U-shape i s most c l e a r . However, some of. the d i f f u s e d s t r u c t u r e Pc3 l i s t e d may behave somewhat d i f f e r e n t l y . B e s i d e s 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 are e v e n t s t h a t have secondary peaks o c c u r r i n g near dawn o r b e f o r e dusk. One such example i s i l l u s t r a t e d i n F i g . I I I . 5 c where two secondary peaks are shown, one at 0600 L.T. and the 5 6 o t h e r a t 1 6 0 0 L.T. The o c c u r r e n c e of a secondary peak around dawn or dusk i s not uncommon a t R a l s t o n . 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 I I I . 6 MIXED CASES OF THE FOUR BASIC TYPES 60 I t has been obse r v e d t h a t the g r e a t m a j o r i t y o f Pc3 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 be s u b c l a s s i f i e d i n t o one o f , or the c o m b i n a t i o n o f , the f o u r b a s i c t y p e s o f d i u r n a l v a r i a t i o n of f r e q u e n c y d e s c r i b e d i n the p r e v i o u s f o u r s e c t i o n s . A t a b l e has been p r e p a r e d where spectrograms over a p e r i o d of t h r e e months i n 1967 have been s u b c l a s s i f i e d a c c o r d i n g t o t h i s scheme (see Table I I I . 3 ) . I n o r d e r t o show the l e v e l of magnetic d i s t u r b a n c e , a s k e t c h has been p r e p a r e d f o r each day i n the t h i r d column of T a b l e I I I . 3 . These s k e t c h e s may p r o v i d e us w i t h a rough i d e a as t o how s t e a d y the p l a n e t a r y magnetic d i s t u r b a n c e i s . But one must bear i n mind the l i m i t a t i o n of Kp i n d e x , and c a r e must be t a k e n b e f o r e one draws f u r t h e r c o n c l u s i o n s . The d e s i g n a t i o n s x^, x^, and x^ s i g n i f y the q u a l i t y 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 p a r t i c u l a r b a s i c t y p e . F o r example, x^ shown under Type 1 would mean t h a t the appearance of the s p e ctrogram f o r t h i s p a r t i c u l a r o b s e r v a t i o n i s b e s t approximated t o Type 1 d i u r n a l v a r i a t i o n . On the o t h e r hand, x^ and x^ shown under Type 2 and Type 4 r e s p e c t i v e l y , i n d i c a t e t h a t t h i s event appears t o behave as a c o m b i n a t i o n of Type 2 and Type 4 d i u r n a l v a r i a t i o n w i t h Type 2 d o m i n a t i n g . Examples are g i v e n i n F i g . I I I . 6 a - e t o demonstrate the e x i s t e n c e of some of the p o s s i b l e c o m b i n a t i o n s . 61 I n F i g . I I I . 6 a , an example i s shown whose d i u r n a l ' v a r i a t i o n may be t a k e n as a c o m b i n a t i o n of the d i s c r e t e i n v e r t e d U-type and the morning and a f t e r n o o n t y p e . The boundary between the morning and a f t e r n o o n t y p e s t a k e s p l a c e around noon and the s p i k e - l i k e s t r u c t u r e i s apparent t h r o u g h o u t most of the day. I n F i g . I I I . 6 b the i n v e r t e d U-type has d i s c r e t e s t r u c t u r e e a r l y i n the morning, but the appearance of the s p e c trogram i s of the d i f f u s e d type a f t e r 1100 L.T. and i n the a f t e r n o o n , A s i m i l a r example i s shown i n F i g . I I I . 6 c where the d i f f u s e d s t r u c t u r e appears i n the morning r a t h e r t h a n i n the a f t e r n o o n . C o m b i n a t i o n of the d i f f u s e d i n v e r t e d U-type w i t h t h e normal type i s demonstrated i n y e t a n o t h e r example shown i n F i g . I I I . 6 d . I n F i g . I I I . 6 e the s p e c t r a l p a t t e r n shown i s so c o m p l i c a t e d t h a t each of the f o u r b a s i c t y p e s of d i u r n a l b e h a v i o u r may be i d e n t i f i e d . 62 TABLE III.3 S U B - C L A S S I F I C A T I O N OF SOME Fc3 EVENTS Da t e 1967 ^ V a r i a t i o n Type 1 Type 2 Type 3 Type 4 M i sc Oct 1 11+ Oct 2 9+ Oct 3 1 5 _ Oct 4 8 0 Oct 5 Oct 6 1 2 o Oct 12 24 + Oct 13 17 1 0 Oct 14 21_ Oct 16 Oct 17 18 0 Oct 18 14_ Oct 19 9 0 Oct 20 6_ Oct 23 Oct 24 Oct 25 \ Oct 26 5_ Oct 27 l 8 o Oct 28 30_ Oct 29 29_ Oct 30 19 J L w - A X 2 x 4 3^ x. x . xn X, X, X, X, v l x. X l3 X 3 X, X, X, x. 3 63 D a t e v K Kp Type 1 Type 2 Type 3 Type 4 1967 p V a r i a t i o n I j .'-^  1 • 1 M i s c . Nov 3 2 ^ o Nov 4 16 + X 2 X 2 Nov 5 X 2 X 2 Nov 6 X 2 Nov 8 Nov 9 18 \. , x 2 x 3 Nov 10 8 0 yv-... x 3 Nov 13 Nov 1 4 19_ X 2 x 3 Nov 15 X 2 X 3 Nov 16 17 ' 0 - X 3 X 2 Nov 17 3 . X l Nov 18 5 0 X l Nov 19 6 + — . X l Nov 20 3 o * x 3 Nov 23 16_ X 2 X 3 Nov 24 27_ - •v_^...-X 2 X 3 Nov 25 x 3 Nov 28 2 4 + x 3 Nov 29 x 3 x 3 x 3 Nov 30 21 x„ X., v 3 x. X. X-X, 64 D a t e _ K p Type 1 Type 2 Type 3 Type 4 1967 / K „ u „ „ , - „ n „ „ 1.-^  I .-X l . - x I .1; :: MiSC p V a r i a t i o n | Dec 4 Dec 5 Dec 6 Dec 7 Dec 8 Dec 9 Dec 10 Dec 11 Dec 12 Dec 13 Dec 19 Dec 20 Dec 21 Dec 22 Dec 24 Dec 25 Dec 27 Dec 28 Dec 29 Dec 30 14. 1L 28 27 31 18 12 5 1 2 c 10_ 31 33. 24 2 1 c 11_ 6 c 1 6 . 9 o + + o o + 10 18 "V A \ X v l 2 2 X, X, X, X., X, X X, X, X. X, v 3 X, X 3 X, X., X 3 X. X. X, 3^ X, 3^ k 2 C3 x. 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 4 OCT 67 MIXED INVERTED U-TYPE OF DISCRETE AND DIFFUSED STRUCTURE 6 7 FIG 111.6c RALSTON X 26 OCT 67 MIXED 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 ALL U BASIC TYPES 70 I I I . 7 MISCELLANEOUS TYPES The d i u r n a l v a r i a t i o n o f Pc3 a t R a l s t o n becomes very-c o m p l i c a t e d when t h e p l a n e t a r y m a g n e t i c c o n d i t i o n s a r e 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 d i s t u r b e d . However, t h e r e s e a r c h u n d e r t a k e n I n t h i s t h e s i s i s c o n c e r n e d o n l y w i t h Pc3 t h a t b e h a v e s u n d e r q u i e t t o m i l d l y d i s t u r b e d c o n d i t i o n s . No a t t e m p t h a s b e e n made t o s t u d y t h e c o n t i n u o u s p u l s a t i o n when t h e d i s t u r b a n c e l e v e l i s h i g h . I n t h e f o l l o w i n g , t h e r e a r e f o u r e x a m p l e s g i v e n I n P i g . I I I . 7 a j b, c, and d t h a t c o u l d n o t be c l a s s i f i e d i n t o any o f t h a t d e s c r i b e d i n t h e p r e v i o u s s e c t i o n . T h e r e a r e , o f c o u r s e , many o t h e r e x a m p l e s . we h a v e n o t i c e d t h a t t h e i r v a l u e s o f i n d e x a r e e i t h e r t o o h i g h o r t h e y a r e v e r y f l u c t u a t i n g . 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 I I I . 8 INTERPRETATION OF RESULTS AND DISCUSSION Many r e s e a r c h e r s b e l i e v e t h a t the Pc4 range o f p u l s a -t i o n i s caused by a hydromagnetic wave, and t h a t t h i s h ydromagnetic wave p r o p a g a t e s a l o n g the f i e l d l i n e a t the plasmapause d i s c o v e r e d by C a r p e n t e r (1966), whereas the Pc3 range o f p u l s a t i o n i s thought o f as 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 the 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 e v i d e n c e p r o v i d e d by H i r a s a w a and Nagata (1966) and Nagata and F u k u n i s h i (1968) g i v e s f u r t h e r s u p p o r t to the above p o s t u l a t i o n s . By s t u d y i n g the d i u r n a l ' v a r i a t i o n o f P c 3 and Pc4 f r e q u e n c y , t h e s e a u t h o r s found agreement between e x p e r i m e n t a l r e s u l t s o b t a i n e d a t Japanese s t a t i o n s 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 . The t h e o r e t i c a l c a l c u l a t i o n i s based on g e n e r a l d i u r n a l b e h a v i o u r o f the plasmapause 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 (1966) u s i n g w h i s t l e r d a t a . As C a r p e n t e r has shown, 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 l a r g e s t a t about 2000 L.T. and the s h o r t e s t a t about 0600 L.T. when the geomagnetic f i e l d i s m o d e r a t e l y d i s t u r b e d ( K p = 2 —» 4). I f the Pc3 range o f p u l s a t i o n i s i n d e e d a s t a n d i n g wave s e t up between the plasmapause and the i o n o s p h e r e , i t s h o u l d behave as a d i u r n a l v a r i a t i o n t h a t has maximum p e r i o d around 2000 L.T. and minimum p e r i o d a t about 0600 L.T. T h i s i s e x a c t l y the case found e x p e r i m e n t a l l y by H i r a s a w a and Nagata (1966). I t may a l s o e x p l a i n the e x i s t e n c e o f one o f the two Pc3 bands o b s e r v e d a t R a l s t o n 76 ( P i g . I l l . 2 b ) . The f r e q u e n c y b a nd t h a t h a s p e r i o d c l o s e s t t o t h a t o b s e r v e d by H i r a s a w a and N a g a t a (35 mHz) i s t h e 38 mHz band shown i n T a b l e I I I . l . I t r e m a i n s f o r u s t o e x p l a i n why t h e r e a r e two Pc3 b a n d s , and why t h e Pc4 b a nd i s a l w a y s o b s e r v e d s i m u l t a n e o u s l y w i t h t h e two Pc3 b a n d s . S t u a r t and U s h e r (1966), and H o l m b e r g (1953), f o u n d t h a t t h e Pc s p e c t r a a t E s k d a l e m u i r ( d> = 58.4°) show p e a k s 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 60 s e c (Pc4) and 25 s e c (Pc3) p e r i o d , and t h e y a t t r i b u t e t h i s t o t h e d i f f e r e n t h a r m o n i c s o f a f u n d a m e n t a l f r e q u e n c y w h i c h shows p r e f e r e n c e a t E s k d a l e m u i r . One w o u l d t h e n b e g i n t o wonder w h e t h e r t h e m u l t i - b a n d s t r u c t u r e o f c o n t i n u o u s p u l s a t i o n e v e n t s o b s e r v e d a t R a l s t o n c o u l d i n t u r n be e x p l a i n e d by t h e p r e s e n c e o f d i f f e r e n t h a r m o n i c s i n v o l v e d . However, i t may be d e m o n s t r a t e d t h a t t h e • t h e o r y o f f e r e d b y S t u a r t and U s h e r f a i l s t o e x p l a i n some o f t h e o b s e r v a t i o n a l f a c t s f o u n d , a l t h o u g h t h e e x i s t e n c e o f m u l t i - b a n d s t r u c t u r e a s a r e s u l t o f d i f f e r e n t h a r m o n i c s c a n n o t be d i s p r o v e d a l t o g e t h e r a s a t h e o r y ( D e r i v a t i o n o f t h i s r e s u l t i s shown i n a p p e n d i x 3 ) • T h e r e f o r e , we have t o l o o k f o r a more f a v o u r a b l e t h e o r y . So f a r , we have p o s t u l a t e d o n l y t h e e x i s t e n c e o f a s t a n d i n g wave a l o n g t h e f i e l d l i n e a t t h e p l a s m a p a u s e and a l s o b e t w e e n t h e p l a s m a p a u s e and t h e i o n o s p h e r e . I f we e x t e n d t h i s p o s t u l a t i o n t o i n c l u d e t h e p o s s i b l e e x i s t e n c e o f a n o t h e r s t a n d i n g wave, s e t up i n t h e p l a s m a - t r o u g h o u t s i d e 7 7 the plasmapause, t h e n the f o l l o w i n g must be c o n s i d e r e d . The p o s i t i o n o f R a l s t o n i s s i t u a t e d v e r y c l o s e t o the f o o t of the f i e l d l i n e d e f i n i n g t h e 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 time when R a l s t o n i s a t the plasmapause which i s v e r y p r o b a b l e 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 , and a t t h a t p a r t i c u l a r i n t e r v a l o f t i m e , t h e r e i s s t a n d i n g wave of p o l o i d a l mode e x i s t i n g i n the plasmasphere, and i n t h e p l a s m a t r o u g h . L e t e i g e n - f r e q u e n c y o f t h e s e s t a n d i n g waves f o r the two r e g i o n s be f ^ and f ^ r e s p e c t i v e l y . B o t h f ^ and f ^ are i n Pc3 f r e q u e n c y range. As a r e s u l t , s u p e r p o s i t i o n of t h e s e two waves would produce an o s c i l l a t i o n o f the magnetic f i e l d o b s e r v e d 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 y i e l d two d i s t i n c t f r e q u e n c i e s f ^ and f ^ . F u r t h e r m o r e , i f the c o n f i g u r a t i o n o f the plasmapause on t h a t p a r t i c u l a r day i s such t h a t R a l s t o n remains i n t h e v i c i n i t y o f the knee 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 t i m e , and t h i s i s p o s s i b l e because th e plasmapause i s a c o n t i n u o u s t h r e e d i m e n s i o n a l boundary, one would expect t o f i n d i n t h a t p a r t i c u l a r time i n t e r v a l 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 f ^ and f ^ . The v a r i a t i o n of f ^ and f ^ would m a n i f e s t the d i f f e r e n t d i m e n s i o n of the plasmasphere and the p l a s m a t r o u g h . To see whether t h i s I s i n d e e d the s i t u a t i o n t h a t l e a d s t o the o c c u r r e n c e o f m u l t i - b a n d s t r u c t u r e d Pc3 o b s e r v e d i n m i d - l a t i t u d e s t a t i o n s , one has t o t a k e s i m u l t a n e o u s o b s e r v a -t i o n s at the h i g h as w e l l as a t the low l a t i t u d e s t a t i o n s . 7o We s h a l l r e p o r t t h e r e s u l t o f some o f t h e s e o b s e r v a t i o n s i n a l a t e r c h a p t e r . I t h a s b e e n w i d e l y r e c o g n i s e d t h a t Pc4 i s a l o c a l i s e d phenomenon t h a t i s c a u s e d b y a s t a n d i n g h y d r o m a g n e t i c wave s e t up a l o n g t h e f i e l d l i n e a t t h e p l a s m a p a u s e . I f t h i s i s t o be a c c e p t e d , t h e n t h e s i m u l t a n e o u s o c c u r r e n c e o f t h e Pc4 ( f ^ ) band w i t h t h e o t h e r two Pc3 b a n d s may a l s o be e x p l a i n e d i n t h e l i g h t o f t h e above p o s t u l a t i o n t h a t R a l s t o n i s a t t h e p l a s m a p a u s e when m u l t i - b a n d s t r u c t u r e t a k e s p l a c e . F i g . I I I . - 8 i s an a t t e m p t t o r e p r e s e n t g r a p h i c a l l y t h e p e r i o d i c e x p a n s i o n and c o n t r a c t i o n o f b o t h 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 o f f ^ and f ^ f r e q u e n c y r e s p e c t i v e l y ( p o l o i d a l o s c i l l a t i o n s ) . Pc4 ( f , f r e q u e n c y ) i s a l s o shown. F I G . I I I . 8 EIGEM OSCILLATIONS I N THE MAGNETOSPHERE The o c c u r r e n c e o f t h e n o r m a l t y p e d i u r n a l v a r i a t i o n w i t h m o r n i n g and a f t e r n o o n s e p a r a t i o n may a l s o be e x p l a i n e d u s i n g . t h e same m o d e l a f t e r t a k i n g i n t o a c c o u n t t h e dawn-dusk a s y m m e t r y o f t h e p l a s m a s p h e r i c c o n f i g u r a t i o n ( C a r p e n t e r 1966)0 On t h e d a y t h a t t h i s t y p e o f Pc3 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 , 79 R a l s t o n i s o u t s i d e t h e p l a s m a s p h e r e i n t h e m o r n i n g . The 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 t y p e o f Pc3 w o u l d t h e r e f o r e be t a k e n a s e v i d e n c e o f b o u n d a r y c r o s s i n g when R a l s t o n i s g o i n g f r o m o u t s i d e t o t h e i n s i d e o f t h e p l a s m a -s p h e r e . 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 b e t w e e n t h e m o r n i n g and t h e a f t e r n o o n t y p e may be u n d e r s t o o d w i t h t h e same r e a s o n i n g we o f f e r t o e x p l a i n t h e o c c u r r e n c e o f m u l t i - b a n d Pc3. A f t e r c r o s s i n g t h e b o u n d a r y i n t o t h e p l a s m a s p h e r e , t h e m o r n i n g t y p e b e g i n s 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 a s i s a p p a r e n t a t R a l s t o n . The f r e q u e n c y o f Pc3 o b s e r v e d a t R a l s t o n w o u l d now d e p e n d on t h e d i m e n s i o n o f t h e i n s i d e o f t h e p l a s m a s p h e r e . T h e r e f o r e , t h e f r e q u e n c y o f t h e a f t e r n o o n t y p e Pc3 w o u l d d e c r e a s e r a p i d l y w i t h t i m e . T h i s a g r e e s w i t h e x p e r i m e n t a l r e s u l t s r e p o r t e d e a r l i e r i n t h i s c h a p t e r . The i n v e r t e d U - p a t t e r n o f t h e m o r n i n g t y p e Pc3 w i t h maximum f r e q u e n c y o c c u r r i n g a r o u n d 0600 L.T. c o u l d be e x p l a i n e d t o o i f t h e r e g i o n o u t s i d e t h e p l a s m a p a u s e a l s o h a s an e a s t - w e s t a s y m m e t r y . R e c e n t l y , . S i s c o e e t a l (1969), u s i n g d a t a o b t a i n e d f r o m t h e M.I.T. p l a s m a e x p e r i m e n t on P i o n e e r 6, f o u n d t h a t an e a s t - w e s t a s y m m e t r y may e x i s t i n t h e s o l a r w i n d v e l o c i t y . The a s y m m e t r y i s i n t r o d u c e d b y t h e i n f l u e n c e o f t h e s u n ' s r o t a t i o n on t h e i n t e r a c t i o n b e t w e e n f a s t and s l o w p l a s m a s t r e a m s . The f a s t s t r e a m w o u l d t e n d t o come f r o m t h e w e s t and the slow one from the e a s t v/ith r e s p e c t t o the average s o l a r wind d i r e c t i o n . The e x i s t e n c e of an eastward component of s o l a r wind v e l o c i t y would produce an e a s t -west asymmetry of the magnetosphere. As the magnetosphere i s s u b j e c t e d t o c o m p r e s s i o n by s o l a r wind w i t h an e a s t w a r d v e l o c i t y component, the d i m e n s i o n on the dawn s i d e of the magnetosphere o u t s i d e the plasmasphere would be s m a l l e r t h a n t h a t on t h e a f t e r n o o n s i d e . The r e g i o n o u t s i d e the plasmapause 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 because of i t s low 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 f u r t h e r e x p e r i m e n t a l s u pport t o the t h e o r y we o f f e r e d t o e x p l a i n the 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 and a f t e r n o o n s e p a r a t i o n . 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 o f f r e q u e n c y of Pc3 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 c c u r r e d o n l y under m a g n e t i c a l l y q u i e t c o n d i t i o n s . C a r p e n t e r (1967) observed t h a t d u r i n g v e r y q u i e t p l a n e t a r y magnetic c o n d i t i o n the plasmapause appears t o assume a more n e a r l y c i r c u l a r c o n f i g u r a t i o n a t I t s l a r g e r r a d i u s . A c c o r d i n g t o t h i s r e p o r t the d i m e n s i o n o f the plasmasphere becomes so l a r g e under 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 would be found i n s i d e the plasmasphere t h r o u g h o u t the day. That I s t o say, no boundary c r o s s i n g s h o u l d be o b s e r v e d , To e x p l a i n the i n v e r t e d U-type d i u r n a l b e h a v i o u r , one has t o go back t o the t h e o r y of the f o r m a t i o n of t h e plasmapause. 81 The f o r m a t i o n o f plasmapause has been t h e o r e t i c a l l y i n t e r p r e t e d ( N i s h i d a , 1966) as due t o a s u p e r p o s i t i o n of the two d i f f e r e n t k i n d s of dynamic m o t i o n o f the m a g n e t o s p h e r i c .plasma, namely the c o - r o t a t i o n w i t h the E a r t h and the 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 s o l a r w ind. The mechanism 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 the c o n v e c t i v e m o t i o n i n the magnetosphere i s b e s t d e s c r i b e d i n terms o f Dungey's model (1961). I t has been shown by Nagata (1967) t h a t .the p o l a r S P - f i e l d which i s c o n s i d e r e d as caused by the magnetospheric 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 the Kp i n d e x approaches z e r o . T h i s r e s u l t 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 be no i n t e r a c t i o n between the s o l a r wind and the magnetospheric plasma, whence the s o l a r wind p r e s s u r e causes s i m p l y a c o m p r e s s i o n o f the magnetosphere i n c l u d i n g the plasmapause on the noon s i d e , t h u s making the e i g e n f r e q u e n c y of the s t a n d i n g hydromagnetic wave of m o d i f i e d A l f v e n mode i n s i d e the plasmasphere l a r g e s t around noon, t h a t i s , an i n v e r t e d U-type o f d a i l y v a r i a t i o n . The dawn s i d e s h i f t of the maximum f r e q u e n c y and a l s o o f the boundary between morning and a f t e r n o o n type o f Pc3 c o u l d a l s o be e x p l a i n e d by N i s h i d a ' s t h e o r y of the plasma-pause when the value, o f the Kp i n d e x becomes l a r g e r , AS N i s h i d a has a l r e a d y shown, the l o c a l t i me c o r r e s p o n d i n g t o the minimum g e o c e n t r i c d i s t a n c e o f the plasmasphere s h i f t s towards the dawn s i d e as the c o n v e c t i v e motion i s i n t e n s i f i e d . 8 2 T h i s a g a i n agrees w i t h e x p e r i m e n t a l r e s u l t s mentioned i n the p r e v i o u s s e c t i o n s . 33 CHAPTER I V K„-DEPENDENCE OF Pc3 I N MID-LATITUDE _p . , IV.1 INTRODUCTION By c o m p a r i s o n o f t h e p o s i t i o n o f t h e m a g n e t o -s p h e r i c b o u n d a r y , a s d i r e c t l y o b s e r v e d b y t h e E x p l o r e r 12 s a t e l l i t e , w i t h c o r r e s p o n d i n g i n d i c e s , C a h i l l and Amazeen (1963) o b s e r v e d an i n v e r s e r e l a t i o n b e t w e e n Kp and t h e r a d i u s o f t h e m a g n e t o s p h e r e . I f t h e Pc3 r a n g e o f p u l s a t i o n i s c a u s e d b y s t a n d i n g waves o f m o d i f i e d A l f v e n mode e x i s t i n g i n t h e m a g n e t o s p h e r i c r e s o n a t o r s , s i n c e t h e e i g e n f r e q u e n c y o f t h e p o l o i d a l o s c i l l a t i o n d e p e n d s on t h e d i m e n s i o n o f i t s r e s o n a t o r s , one w o u l d e x p e c t t o f i n d d e p e n d e n c e o f t h e f r e q u e n c y o f Pc3 p u l s a t i o n o n t h e Kp i n d e x ( B o l s h a k o v a and T r o i t s k a y a , 1964; B o l s h a k o v a , 1965a; N a g a t a e t a l , 1966). The r e s e a r c h t o be r e p o r t e d i n t h i s c h a p t e r h a s b e e n m o t i v a t e d by a d e s i r e t o f i n d t h e p r e c i s e c o n d i t i o n u n d e r w h i c h t h e 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 o f Pc3 f r e q u e n c y s u b c l a s s i f i e d i n t h e l a s t c h a p t e r may be e x p e c t e d t o o c c u r . F u r t h e r , i f t h e p h y s i c a l n a t u r e o f t h e m e c h a n i s m r e s p o n s i b l e f o r t h e e x i s t e n c e o f e a c h o f t h e Pc3 b a n d s o b s e r v e d a t R a l s t o n i s t o be b e t t e r u n d e r s t o o d , a p r e c i s e k n o w l e d g e must be o b t a i n e d o f how d i f f e r e n t l e v e l s o f m a g n e t i c a c t i v i t y c o u l d a f f e c t e a c h o f t h e i n d i v i d u a l b a n d s . 84 C o r r e l a t i o n between the f r e q u e n c y o f Pc3 p u l s a t i o n and the Kp i n d e x has been found e x p e r i m e n t a l l y by many r e s e a r c h e r s ( M c N i c o l and Ma i n s t o n e , 1963; Nagata and F u k u n i s h i , 1968; B o l s h a k o v a , 1965). B o l s h a k o v a (1965) o b s e r v e d an i n v e r s e dependence o f the Pc p e r i o d s (Pc2, Pc3 and Pc4) on Kp which i s g i v e n by an 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 p Nagata and F u k u n i s h i (1968) a l s o found an a p p r o x i m a t e l y l i n e a r r e l a t i o n between the e i g e n f r e q u e n c y o f magnetic p u l s a t i o n and t h e average v a l u e o f Kp (Kp) as w e l l as ][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 e x p r e s s i o n f o r the maximum c e n t r a l f r e q u e n c y ( f m ) o f Pc3 and Pc4 p u l s a t i o n s which i s g i v e n by f m (mHz) = 11 + 4.5 K f o r the-15 mHz Pc4 band f m (mHz) = 2 0 + 7 Kp f o r the 35 mHz Pc3 band Both e q u a t i o n s w i l l be p l o t t e d i n F i g . IV.2a i n the nex t s e c t i o n . 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 between the maximum c e n t r a l f r e q u e n c y o f each o f the Pc3 bands o b s e r v e d a t R a l s t o n and Kp has been o b t a i n e d . Each o f the t h r e e Pc3 bands d e s c r i b e d i n the l a s t c h a p t e r has been found t o behave d i f f e r e n t l y s u b j e c t t o d i f f e r e n t l e v e l s o f magnetic d i s t u r b a n c e s . Such d i f f e r e n c e s have been s t u d i e d i n the l i g h t 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 a u t h o r s . 85 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 o f Pc3 f r e q u e n c y h ave b e e n f o u n d t o o c c u r u n d e r d i f f e r e n t m a g n e t i c c o n d i t i o n s . The r e s u l t o f t h i s o b s e r v a t i o n w i l l be p r e s e n t e d i n t h e n e x t s e c t i o n . E x p e r i m e n t a l e v i d e n c e g a t h e r e d i n s e c t i o n I V . 3 h a s shown t h a t 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 may o c c u r w i t h an a b r u p t i n c r e a s e i n t h e v a l u e o f t h e Kp i n d e x . An i n t e r -p r e t a t i o n o f o b s e r v a t i o n a l f a c t s I s o f f e r e d i n t h e l a s t s e c t i o n . 86 IV.2 K p - DEPENDENCE OF THE Pc3 FREQUENCY I n o r d e r t o i n v e s t i g a t e how t h e mean f r e q u e n c y o f e a c h o f t h e t h r e e Pc3 b a n d s f„, f ~ and f.. w o u l d r e s p o n d t o d i f f e r e n t m a g n e t o s p h e r i c c o n d i t i o n s r e p r e s e n t e d b y d i f f e r e n t v a l u e s o f K^, e x t r e m e c a r e must be t a k e n t o e n s u r e r e l i a b l e i d e n t i f i c a t i o n o f e a c h o f t h e s e b a n d s u n d e r c o n s i d e r a t i o n . S u c h I d e n t i f i c a t i o n i s made o n l y a f t e r t h e t y p e o f d i u r n a l p a t t e r n i n Pc3 s p e c t r a l s t r u c t u r e I s d e t e r m i n e d and Pc-3 s i g n a l s a r e p r o p e r l y i n t e r p r e t e d w i t h t h e h e l p o f t h e m o d e l i n C h a p t e r I I I . T h u s , t h e v a r i a t i o n o f Pc3 f r e q u e n c i e s w i t h K i s m e a n i n g f u l o n l y i f d a y s w i t h a c o n s t a n t K a r e P P i n v e s t i g a t e d and o n l y w i t h s u c h a c a r e f u l p r e l i m i n a r y s e l e c t i o n may d e f i n i t e and r e l i a b l e e v i d e n c e o f s y s t e m a t i c b e h a v i o u r be o b t a i n e d . I n t h i s c h a p t e r , we s h a l l s e l e c t o n l y t h o s e d a y s t h a t have a p p r o x i m a t e l y c o n s t a n t v a l u e o f K^ f o r o u r b a s i c d a t a . The w o r k i n g c r i t e r i o n I s s u c h t h a t f l u c t u a t i o n o f t h e v a l u e o f t h e Kp i n d e x w i t h i n an i n d i v i d u a l d a y s h o u l d n o t e x c e e d one, t h a t i s , f o r a d a y l a b e l l e d K = 1, t h e v a l u e o f Kp w i t h i n t h a t p a r t i c u l a r d a y must be w i t h i n t h e r a n g e o f L = 0 t o L = 2. F u r t h e r , e a c h o f t h e e x t r e m e c a s e s must n o t o c c u r more t h a n t w i c e a d a y . D a t a c o m p i l e d v / i t h t h e above m e n t i o n e d c r i t e r i o n a r e l i s t e d i n T a b l e IV.1, where t h e v a l u e s o f Kp a s w e l l a s t h e v a l u e s o f Z K f o r e a c h i n d i v i d u a l d a y s e l e c t e d a r e - t a b u l a P a l o n g w i t h t h e mean f r e q u e n c y o f e a c h Pc3 band o b s e r v e d . TABLE IV.1 K o DEPENDENC (TV OF DIURNAL VARIA TION CF Pc 3 Date 1 2 3 K P 4 5 6 V l 8 J '3 (mHs) (n iHz) 1 Type 2 3 0 31 J u l y 67 ° + °+ X 0 0 ° + °+ ° + °+ No Pc3 0 10 Feb 67 0 o X °+ 1_ 1_ °o 0 0 0 o 3o 32 X l 0 17 Nov 67 1_ 1_ °+ 0 0 °+ 0 0 0 i o + 3_ 30 X l 0 18 Nov 67 1 0 1_ 1_ 1_ ° + 1_ °+ 0, T 29 X l 1 25 Oct 67 1_ o, - r 1_ 1 0 ° + 1_ 1 o 1_ X 30 X l 1 20 Oct 67 1 + ° + 1_ 1_ 1 o °+ 1 o 6 _ 30 X l 1 19 Nov 67 1_ 2_ 1_ 1_ °+ i , - r 1 o 0 o 6~ + 30 X l 1 25 Mar 67 °+ 1 o 1, T 1_ X 1_ 1 0 1_ 32 X l 1 20 June 67 I X 2 o 1_ 1 0 1_ 1_ 1_ 8_ 30 X l 1 2 Mar 67 0 o X 1_ 1 + 2_ 1_,_ 1_ 2_ 8~ + 35 X l 1 24 Oct 67 0 0 1 o 1 i ~r 1 + X 1 O 1 o 1_ 9_ 32 X l 1 21 June 67 ° + X 2 o 1 o X X 1 o 1+ 32 X l 1 6 Nov 67 1 + X 2_ 1 + 1_ 1 0 1 + % 23 X l 1 17 Mar 67 2_ X ° + X X 2_ 1, T X 32 X l 1 9 May 67 1 o 1 + 2_ 1 + X 1 + 1_ 1 0 10_ 37 X l 4 8 8 -3-Q) r o v. a , -CM H l/h -=3" OO N CO vo oo 00 rH 00 OJ OO 00 X X X X 00 OO 00 OO OJ OO X X X X X oo o j oo oo OJ X X X X X o in o t- vo -rt -3" IIO -cj- -=3" o N m h i n OO 0") OO 0 0 oo o i + o o oo m m t — co r-\ r-i r-\ r-\ r-i + O O I O 00 i - | OO 00 OJ + O I + O 00 OJ OJ rH OO + + O O O OJ OJ 00 00 OO I I o + o OJ OJ OJ OJ OJ O I + I I OJ OJ OJ OJ 00 I O I J - I r—I 00 00 00 OO o + o + + rH OJ H 0 0 OJ I I I + + r—I OJ OO 00 OJ 00 OJ x x OJ OJ OJ OJ X X X X 0 0 OO OO OJ X X X X h in s vo -3- .^t-IA in co oo oo oo oo O 1 + o O O CO H 00 OJ |—I OJ I O I o OO OJ i H -^ 3" I o o o OO OJ OO oo o + o o OJ OJ OO oo + o O I OJ OJ oo oo I + O I OJ OJ OJ oo o o O I OJ 00 OJ OO + o o o oo oo OJ OJ + O I o oo ^ oo OJ OO OJ X X oo oo X X i n oo i n i n 00 o -=1- -=3-o o vo i n OJ OJ o I 0 0 oo + oo .3 -+ o oo oo I + -=r-o + oo OJ + i oo oo + I oo oo o o .=t oo OJ OJ X X OJ OJ X X i n co vo vo OJ o + r - H OJ oo O I OJ + + oo i n o o -3- -=t I o -=}- 0 0 + o oo oo I + O I OO -=j-+ I rH X 00 X i n vo VD OO oo m + -3-+ -=r-+ -3-+ m co 0 0 oo i n i n VD • + m m i n o -=3-00 CO o Ln O VD 00 vo ^ VD VD OO + o 00 + U OJ m o + OJ vo OJ o . o c - r - vo t — 0 - VD 0 -vo vo vo vo VD VO VD VO vo VO VO VO VO VD vo o -p -P •p a , -P 50 > hO ,Q > o u o o o o OJ ro a > O o ro CD o CD CO c u CD CD CD CD ro P CO o < < p p p P P CO -=3" m VD oo VD OO OJ CO t - CO VO O O OJ OJ H rH rH OJ OJ OJ OJ OJ OJ OO r o OO OO oo -3- -3-a , 00 OJ OJ OJ OJ 1 1 1 1 oo oo 1 1 i n vo OJ OJ OJ 00 oo oo 89 I t h a s b e e n n o t i c e d t h a t no Pc3 a c t i v i t y i s o b s e r v e d d u r i n g e x t r e m e l y q u i e t c o n d i t i o n s . J u l y 31, 1967 i s one o f t h o s e e x t r e m e l y q u i e t d a y s where t h e z e r o v a l u e o f t h e K i n d e x h a s b e e n p e r s i s t e n t t h r o u g h o u t most o f t h e t w e n t y -P f o u r h o u r s . S u c h e x t r e m e l y q u i e t c o n d i t i o n s o c c u r o n l y r a r e l y . As t h e v a l u e o f i n c r e a s e s , t h e mean f r e q u e n c y o f t h e Pc3 band a l s o i n c r e a s e s . I t h a s b e e n f o u n d t h a t a t l e a s t f o r t h e v a l u e K l e s s t h a n o r e q u a l t o 4, t h e mean f r e q u e n c y i s d i r e c t l y p r o p o r t i o n a l t o K . T h i s a g r e e s w i t h P what h a s b e e n r e p o r t e d b y N a g a t a and F u k u n i s h i (1968). To d e m o n s t r a t e t h e d e p e n d e n c e o f t h e d a i l y mean f r e q u e n c y o f Pc3 on 2. Kp, an e x a m p l e i s shown i n F i g . I V . 2a where a c o n t i n u o u s s o n a g r a m h a s b e e n d i s p l a y e d c o v e r i n g a s e v e n and o n e - h a l f d a y p e r i o d f r o m December 4, 1967 t o December 12, 1967. A g r a p h o f 2 K a g a i n s t U n i v e r s a l Time h a s b e e n tr p l o t t e d i n t h e u p p e r p o r t i o n o f the.same d i a g r a m . 2.K i s P u s e f u l i n t h i s c a s e f o r i t p r o v i d e s a r o u g h i n d i c a t i o n o f t h e l o n g 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 b o u n d a r y . As s u g g e s t e d b y F i g . IV.2a, i n w a r d movement o f t h e magneto-s p h e r i c b o u n d a r y a p p e a r s t o be t a k i n g p l a c e f r o m December 4 t o December 6 c a u s i n g t h e e i g e n f r e q u e n c y o f m a g n e t i c p u l s a t i o n t o i n c r e a s e . The c o n d i t i o n becomes f a i r l y s t e a d y i n t h e f o l l o w i n g t h r e e d a y s and e v e n t u a l l y assumes a r e v e r s e t r e n d and e x p a n d s r a p i d l y f r o m December 9 o n w a r d . The v a r i a t i o n o f t h e d a i l y mean p e r i o d o f Pc3 f o l l o w s 9 0 c l o s e l y the v a r i a t i o n of the v a l u e o f SK^. The type of d i u r n a l v a r i a t i o n of Pc3 f r e q u e n c y a l s o appears t o change w i t h c h a n g i n g l e v e l of magnetic d i s t u r b a n c e . The changes t h a t take p l a c e r a n g i n g from the normal type w i t h morning and a f t e r n o o n s e p a r a t i o n o f December 7 t o the d i f f u s e d i n v e r t e d U-type t h a t appears on December 1 0 c o r r e s p o n d t o m o d e r a t e l y d i s t u r b e d t o q u i e t 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 of Pc3 d e s c r i b e d i n the l a s t c h a p t e r p l a y s an i m p o r t a n t r o l e i n our st u d y o f the Kp dependence o f f r e q u e n c y of magnetic p u l s a t i o n 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 . I t has been obse r v e d 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 t o 2, the m u l t i - b a n d c h a r a c t e r i s t i c s o f Pc3 b e g i n t o be s i g n i f i c a n t . The r e s u l t o f 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 . The f r e q u e n c i e s f ^ and o b t a i n e d by s c a l i n g the c o n t o u r e d sonagrams show c l e a r l y an upward i n c r e a s e t r e n d as the v a l u e of Kp i n c r e a s e s . S c a l i n g of the mean f r e q u e n c y f rom a sonagram has been found o f t e n t o be d i f f i c u l t p a r t i c u l a r l y when o v e r l a p between two Pc3 bands has t a k e n p l a c e . I n some cas e s one of the two bands o c c u r s o ver a v e r y b r i e f i n t e r v a l o n l y and i t may be of such l o w e r s i g n a l s t r e n g t h t h a t one b e g i n s t o doubt i t s r e a l e x i s t e n c e . The f2| band i s u s u a l l y much weaker i n s i g n a l s t r e n g t h than the f ^ band 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 ( K p < 3 ) As the magnetospheric 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 . F o r the v a l u e of Kp g r e a t e r t h a n 4, the s i g n a l s t r e n g t h o f the f ^ band i s much g r e a t e r t h a n the f ^ band. 91 Tnere I s a l s o a n o t h e r band o f Pc3 ob s e r v e d 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 . I t i s t h e 25 mHz Pc3 band t h a t was r e p o r t e d i n the l a s t c h a p t e r ( T a b l e I I I . l ) . U n l i k e the o t h e r two bands, the f r e q u e n c y o f the f 2 band does not show c l e a r K dependence, a l t h o u g h the maximum i n t e n s i t y o f the f 2 band has been found to o c c u r when K i s a t a p p r o x i m a t e l y 2. A graph o f Kp dependence o f the mean f r e q u e n c y 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 f o r a l l t h r e e bands o f Pc3, namely f g , f g , and f ^ ( F i g . IV.2b). A s i m i l a r r e l a t i o n s h i p r e p o r t e d by Nagata and F u k u n i s h i from K a k i o k a = 2b?o), and B o l s h a k o v a from Borok (0 = 53?0) has a l s o been p l o t t e d on t h e same diagram f o r compa r i s o n . . I t i s most I n t e r e s t i n g t o f i n d t h a t o f a l l the graphs 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 R a l s t o n i s a p p r o x i m a t e l y p a r a l l e l t o the 15 mHz Pc4 band, and not the 35 mHz Pc3 band r e p o r t e d by Nagata and F u k u n i s h i . That i s t o say, the 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 behaves the same way as t h e Pc4 a t K a k i o k a would behave under d i f f e r e n t m a gnetospheric c o n d i t i o n s . A s i m i l a r t r e n d has a l s o been o b s e r v e d f o r the Pc3 band r e c o r d e d by. B o l s h a k o v a when the v a l u e o f K^ i s s m a l l e r t h a n 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 as i t may r e v e a l l o c a t i o n s w i t h i n the magnetosphere where the d i f f e r e n t bands o f Pc3 o b s e r v e d a t R a l s t o n c o u l d have o r i g i n a t e d . 92 I t h a s b e e n n o t i c e d a l s o t h a t i f t h e mean v a l u e o f f m I s t o be p l o t t e d f r o m t h e two f ^ and f ^ c u r v e s f o r e a c h v a l u e o f Kp, t h e r e s u l t a n t c u r v e w o u l d a p p e a r t o be p a r a l l e l t o t h e Pc3 c u r v e g i v e n b y N a g a t a and F u k u n i s h i . I n t h e l a s t t h r e e c o l u m n s o f T a b l e I V . 1 , t h e d i u r n a l v a r i a t i o n o f Pc3 f r e q u e n c y f o r s t e a d y d a y s h a s b e e n c l a s s i f i e d i n t o f o u r t y p e s a c c o r d i n g t o t h e c l a s s i f i c a t i o n scheme p r o p o s e d i n t h e l a s t c h a p t e r . The d e s i g n a t i o n s X - ^ X g and X g u s e d i n T a b l e I I I . 3 i n t h e l a s t c h a p t e r a r e a g a i n u s e d i n T a b l e IV.1 t o s i g n i f y t h e q u a l i t y o f e a c h i n d i v i d u a l e v e n t w i t h r e s p e c t t o e a c h p a r t i c u l a r b a s i c t y p e . I t i s e v i d e n t f r o m t h e T a b l e t h a t t h e d i f f u s e d i n v e r t e d U - t y p e (Type 3 ) o f d i u r n a l v a r i a t i o n o f Pc3 f r e q u e n c y a p p e a r s 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 c o n -d i t i o n i s b o t h q u i e t and s t e a d y (K •< 2), w h e r e a s one o f P o r a m i x t u r e o f t h e o t h e r t y p e s i s t o be o b s e r v e d d u r i n g 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 ( 2 < K C 4 ) . F o r P K p > k, t h e c o n d i t i o n 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 v a r i a t i o n o f Pc3 f r e q u e n c y c o u l d n o t be s i m p l y c l a s s i f i e d . To f u r t h e r i l l u s t r a t e T a b l e I V . 1 , p a r t i c u l a r e x a m p l e s a r e g i v e n i n F i g . IV.2c t o F i g . IV.2g. One e x a m p l e h a s b e e n g i v e n f o r e a c h d i f f e r e n t v a l u e o f f r o m 0 t o 4. The g e n e r a l a p p e a r a n c e o f t h e e x a m p l e s g i v e n i n F i g . IV.2c and F i g . IV.2d i s v e r y s i m i l a r . T hey b o t h b e h a v e a s d i f f u s e d U - t y p e d i u r n a l v a r i a t i o n . 93 The example given i n Pig. IV.2e f o r Kp = 2 displays clear multi-band structure with s p i k e - l i k e discrete appearance. The discrete appearance i s a feature common to a l l cases under moderately quiet conditions (K i s between 2 and 3) or when the condition i s quiet and unsteady (see Section III.4). Tne March 27 event shown i n F i g . IV.2f f o r K p = 3 shows a normal type of diurnal v a r i a t i o n of frequency. The separation between the morning and afternoon type of Pc3 i s not at a l l c l e a r on the ordinary sonagram because the two bands overlap around and a f t e r 1400 L.T. causing confusion. However, the contoured sonagram displayed i n the lower portion of the diagram reveals 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 Pc3 frequency which has morning and afternoon separation 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 given i n F i g . III. 3 a In the l a s t chapter. Unlike the event of October 18, 1967 which occurred under moderately quiet conditions, the event shown i n F i g . IV.2g took place when the magnetic condition was reasonably disturbed. Further, the December 26, 1966 event displays double p e r i o d i -c i t y i n the morning as well as i n the afternoon, contrary to that observed on October 18, 1967. 4 0 , 3 0 -20 -10 0 J 1 1 1 1 1 1 1 1 1 1 1 1 -+ F I G . I V . 2 a Z K p D e p e n d e n c e o f t h e P c 3 M e a n F r e q u e n c y F I G . I V . 2 b K p D e p e n d e n c e a t R a l s t o n 4> = 5 8 . 8 FIG.IV.2c RALSTON X b NOVEMBER 18 1967 Kp = 0 FKS.IV.2d RALSTON X b May 10 .1967 K p = 1 FG.IV.2e RALSTON X b October 5, 1967 Kp - 2 U.T. 6 8 K> 12 14 16 18 20 22 00 2 4 — I . [ • I . I • | • I • I • I • 1 • I • I • I L.T. 23 1 11 13 15 17 19 21 23 1 TVP« • •» SOMAQHAM • KAY «L*CTIIIC CO. PIN* ITOOK. H. J. FC.IV.2f RALSTON Xb March 27,1967 Kp - 3 FIG. IV. 2g RALSTON X b December 26, 1966 Kp = 4 101 IV.3 SUDDEN ENHANCEMENT OF Pc3 ACTIVITY Dependence of the a m p l i t u d e o f Pc3 p u l s a t i o n on the Kp i n d e x has been r e p o r t e d by many a u t h o r s (Maple, 1959; Campbell, 1959; Munch, 1964; M c N i c o l and M a i n s t o n e , 1963). These a u t h o r s observed t h a t the a m p l i t u d e of Pc3 o s c i l l a t i o n i n c r e a s e s w i t h a r i s e i n the Kp i n d i c e s . A s i m i l a r t r e n d of Kp dependence of the a m p l i t u d e o f Pc3 i s g e n e r a l l y e v i d e n t a t R a l s t o n . The a m p l i t u d e o f Pc3 o s c i l l a t i o n u s u a l l y i n c r e a s e s w i t h a r i s e i n the l e v e l o f magnetic d i s t u r b a n c e as may be i l l u s t r a t e d i n F i g . IV.2a o f the l a s t s e c t i o n . But the Kp i n d e x , or i n t h i s case the v a l u e o f 2 Kp, c o u l d o f f e r i n d i c a t i o n of l o n g range movement of the magnetospheric boundary and the g e n e r a l d i s t u r b a n c e l e v e l w i t h i n the magnetosphere; any s h o r t range movement i n the v a l u e o f the Kp i n d e x would not u s u a l l y r e s u l t i n a c o r r e s p o n d i n g change of the a m p l i t u d e o f Pc3. An example i s shown i n F i g . TV.3a where the Kp i n d e x has i n c r e a s e d from the v a l u e o f 1 t o t h e v a l u e o f 3 i n t h e a f t e r n o o n and y e t , no s i g n i f i c a n t i n c r e a s e i n Pc3 a c t i v i t y has been o b s e r v e d . However, t h e r e are a few o c c a s i o n s when sudden enhancement of Pc3 a c t i v i t y has been o b s e r v e d t o t a k e p l a c e f o l l o w i n g a s i m i l a r r i s e i n the v a l u e o f the K^ i n d e x . Two examples are i n d e p e n d e n t l y d i s p l a y e d i n F i g . IV.3b and F i g . IV.3c t o demonstrate the w o r k i n g of the phenomenon. 102 I n F i g . IV.3b, an ab r u p t I n c r e a s e o f Pc3 a m p l i t u d e , I n d i c a t e d by an i n c r e a s e i n da r k n e s s o f the sonagram, has been obser v e d a t a p p r o x i m a t e l y 2100 U.T. May 21, 1967 which i s the time w i t h i n the t h r e e hour i n t e r v a l when the K p i n d e x has r i s e n from a v a l u e o f 1 Q t o 3+. 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 t a k e s p l a c e i n t h e Pc3 band o n l y (25-60 mHz i n the case o f the May 21 e v e n t ) . I n F i g . IV.3c, a n o t h e r example o f sudden enhancement o f Pc3 a c t i v i t y c o r r e s p o n d i n g to an i n c r e a s e i n the K p i n d e x i s shown where two Pc3 bands have been i n i t i a t e d . N o t i c e t h a t an enhancement o f Pc4 a c t i v i t y o c c u r s p r i o r t o the enhancement o f b o t h o f the Pc3 bands which t a k e s p l a c e a t a p p r o x i m a t e l y 1830 U.T. Two c a l i b r a t i o n marks appear on the sonagram b e f o r e and a t 1723 U.T. 103 FIG. IV.3o RALSTON x K AUGUST 9 , 1967 104 U T 6 8 10 12 1 4 1 6 1 8 2 0 2 2 0 2 4 6 8 - | , | , [ , | • [ I • 1 • I • I ' I ' I ' l l L.T. 2 3 1 3 5 7 9 11 1 3 1 5 17 1 9 2 1 2 3 1 11ft. m, «a soNAaitAM • K A T K I _ I C T K I C C O . rms. B R O C K H. J. R A L S T O N X b M A Y 2 2 . 1 9 6 9 F I O . I V . 3 b S U D D E N E N H A N C E M E N T O F Pc 3 1 0 5 FIG. IV.3c RALSTON Xb AUGUST 23, 1967 SUDDEN ENHANCEMENT OF Pc3 A Pc4 106 IV.4 DISCUSSION B a s e d o n d a t a o b t a i n e d on b o a r d M a r i n e r 2, S n y d e r e t a l (1963) h a v e d e r i v e d an e m p i r i c a l e x p r e s s i o n d e m o n s t r a t i n g t h e 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 X K and t h e P v e l o c i t y o f t h e s o l a r w i n d . W i l c o x e t a l (1964) a l s o h a v e d e r i v e d f r o m t h e IMP - 1 o b s e r v a t i o n t h a t t h e r e i s an a p p r o x i m a t e l y l i n e a r r e l a t i o n b e t w e e n V and K . S i n c e i t i s n o t i n c o n c e i v a b l e t h a t t h e p l a s m a s p h e r e o r magneto -s p h e r e more c o m p r e s s e d b y t h e s t r o n g e r s o l a r w i n d , c o r r e s -p o n d i n g t o an i n c r e a s e i n t h e K i n d i c e s , may r e s u l t i n a s h o r t e r p e r i o d o f h y d r o m a g n e t i c e i g e n o s c i l l a t i o n a s i n d i c a t e d f o r t h e c a s e o f Pc5 o s c i l l a t i o n ( H i r a s a w a e t a l , 1 9 6 6 ) , a d i r e c t c o r r e l a t i o n b e t w e e n K and t h e f r e q u e n c y o f Pc t y p e o f m a g n e t i c p u l s a t i o n h a s b e e n a n t i c i p a t e d . E x p e r i m e n t a l o b s e r v a t i o n h a s so f a r c o n f i r m e d t h i s t h e o r e t i c a l s p e c u l a t i o n . F u r t h e r , i f t h e e x i s t e n c e o f t h e m u l t i - b a n d s t r u c t u r e d 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 t h e m o d i f i e d A l f v e n mode s e t up i n t h e e a r t h m a g n e t i c r e s o n a t o r s b o t h i n s i d e t h e p l a s m a s p h e r e and I n t h e p l a s -m a t r o u g h , one w o u l d e x p e c t t h e e i g e n o s c i l l a t i o n s i n t h e two d i f f e r e n t r e s o n a t o r s t o r e s p o n d d i f f e r e n t l y t o any change i n m a g n e t o s p h e r i c c o n d i t i o n s . As t h e p l a s m a t r o u g h i s more s u s c e p t i b l e t o t h e c o m p r e s s i o n o f t h e s o l a r w i n d b e c a u s e o f i t ' s l o w p a r t i c l e d e n s i t y , one may a n t i c i p a t e 107 t h a t t h e Pc3 o r i g i n a t i n g i n t h e p l a s m a t r o u g h w o u l d b e m o r e s e n s i t i v e t o a n y c h a n g e o f t h e K p i n d e x t h a n i t s c o u n t e r p a r t i n t h e p l a s m a s p h e r e . T h e a b o v e c o n s i d e r a t i o n l e a d s u s t o b e l i e v e t h a t t h e f ^ s u b - b a n d o f Pc3 p u l s a t i o n o r i g i n a t e s i n t h e p l a s m a t r o u g h o u t s i d e t h e p l a s m a p a u s e w h e r e a s t h e f ^ s u b - b a n d o r i g i n a t e s i n s i d e t h e p l a s m a -s p h e r e . T h e o b s e r v a t i o n a l f a c t t h a t t h e f ^ c u r v e s h o w n i n F i g . I V . 2 b i s p a r a l l e l t o t h e Pc4 c u r v e g i v e n b y N a g a t a e t a l p r o v i d e s f u r t h e r s u p p o r t f o r o u r s p e c u l a t i o n t h a t t h e f ^ s u b - b a n d o f Pc3 o r i g i n a t e d f r o m t h e i n s i d e o f t h e p l a s m a p a u s e . I f Pc4 i s c a u s e d b y a h y d r o m a g n e t i c w a v e . p r o p a g a t i n g a l o n g t h e f i e l d l i n e a t t h e p l a s m a p a u s e , t h e f r e q u e n c y o f t h i s e i g e n o s c i l l a t i o n w o u l d r e f l e c 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 w h i c h i s b o u n d e d b y t h e p l a s m a p a u s e . A s 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 , a n d i n t u r n t h e p l a s m a s p h e r e , c h a n g e s u b j e c t t o d i f f e r e n t d e g r e e s o f c o m p r e s s i o n b y t h e s o l a r s t r e a m s , i t i s o n l y l o g i c a l t o e x p e c t c l o s e c o r r e l a t i o n b e t w e e n t h e c h a n g e o f t h e f r e q u e n c y o f t h e Pc4 ( f - ^ ) b a n d a n d t h e c h a n g e o f t h e f r e q u e n c y o f t h e f ^ b a n d o f Pc3 u n d e r d i f f e r e n t l e v e l s o f m a g n e t i c a c t i v i t y . A l s o , t h e f ^ b a n d i s f o u n d t o b e s i g n i f i c a n t o n l y w h e n t h e m a g n e t i c c o n d i t i o n i s r e a s o n a b l y d i s t u r b e d ( K p ~ 3 ) j t h a t i s , w h e n R a l s t o n i s w e l l o u t s i d e t h e p l a s m a p a u s e . O n t h e o t h e r h a n d , w h e n t h e m a g n e t i c c o n d i t i o n 108 i s quiet Ralston would be i n s i d e the plasmasphere and the only dominating p u l s a t i o n observed would be i n the i\ band. This observation again i s c o n s i s t e n t with our proposed model. The f band of Pc3 described i n S e c t i o n I I I . 2 of the l a s t chapter has not demonstrated c l e a r K^-dependence. This property may be v i t a l i n our u l t i m a t e understanding of the exact nature of the f band of P c 3 . The present author b e l i e v e s , as many others do, that 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 hydrornagnetic o s c i l l a t i o n i n the dayside magnetosphere. Thus, an enhancement of P c 3 a c t i v i t y may then be t a k i n g place. The example given i n P i g . IV.3 c suggests t h i s p o s s i b i l i t y . The sudden enhancement of a c t i v i t y f o r the August 23 event took place f i r s t i n the Pc4 frequency range which i s then followed by an e x c i t a t i o n of the two Pc3 bands. This may suggest that t h i s kind of sudden enhancement begins with 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 obtained i s not s u f f i c i e n t f o r us to draw any conclusions, and f u t u r e research should look i n t o the p o s s i b i l i t y of simultaneous observations 109 b e i n g made at two s t a t i o n s a p p r o x i m a t e l y l8o° a p a r t i n geomagnetic l o n g i t u d e . 110 CHAPTER V COMPARATIVE STUDIES OF Pc3 IN HIGH AND MID-LATITUDES V . l INTRODUCTION In order to understand the o r i g i n of micropul-s a t i o n , i t i s of prime importance to determine a c c u r a t e l y any r e g u l a r i t i e s that govern the changes of mi c r o p u l s a t i o n amplitude and period with 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 earth's surface. Although a tremendous amount of work has been done by numerous researchers on t h i s subject since the IGY, and undoubtedly great advances have been made i n the past decade through 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 techniques, there i s not yet a c o n s i s t e n t p i c t u r e that could 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 reported by d i f f e r e n t workers. T h e o r e t i c a l attempts to formulate the nature of a l a t i t u d e dependence, based on hydromagnetic resonances of the magnetosphere, were made by Dungey (1954) and Kato and v/atanabe (1956a). Dungey's c a l c u l a t i o n s have been extended by Westphal and Jacobs (1962) to include more recent knowledge of the magnetosphere. Each of 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 steady increase i n the period of mi c r o p u l s a t i o n with an increase i n geomagnetic l a t i t u d e . I l l Indeed, e a r l i e r experimental o b s e r v a t i o n s made by v a r i o u s authors have a l s o provided support f o r the t h e o r e t i c a l p r e d i c t i o n t h a t the p e r i o d s of Pc2, 3* and 4 types of continuous p u l s a t i o n i n c r e a s e with an i n c r e a s e i n l a t i t u d e . By s t u d y i n g simultaneous r e c o r d s around the world, Obayashi and Jacobs (1958) f i r s t r e p o r t e d the systematic i n c r e a s e of m i c r o p u l s a t i o n p e r i o d with l a t i t u d e (j) and concluded t h a t the p e r i o d i s i n v e r s e l y p r o p o r t i o n a l to cos 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 found by Bolshakova and Zybin upon s t u d y i n g the p e r i o d s of the most s t a b l e p u l s a t i o n s at each of the f i v e s t a t i o n s w i t h i n the l a t i t u d e range 23°N-»64°N ( T r o i t s k a y a , 1967) . However, the r e s u l t r e p o r t e d by Obayashi and Jacobs was d e r i v e d from data obtained from the nighttime as w e l l as from the daytime side of the e a r t h , and i t may not h o l d f o r the p u r e l y daytime Pc3 events that we assume today. More recent o b s e r v a t i o n s c r e a t e d more c o n f u s i o n than they o r i g i n a l l y planned to r e s o l v e . I n v e s t i g a t i o n s on the l a t i t u d e dependence of the Pc3 p e r i o d made by Duncan (1961) and E l l i s (i960) with the same data from three s t a t i o n s i n l a t i t u d e range 29°S - 52°S gave c o n t r a d i c t o r y r e s u l t s , while other authors, n o t a b l y Herron and H e i t z l e r (1966), Usher and S t u a r t (1966), and T r o i t s k a y a (1967) f a i l e d to o b t a i n a c l e a r p i c t u r e of the dependence of Pc3 p e r i o d on l a t i t u d e . They have reported t h a t i n s t a n c e s when somewhat longer p e r i o d s are observed at high l a t i t u d e occur j u s t as o f t e n as i n s t a n c e s when the reverse a p p l i e s . 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 rapid-run magnetograms at Great Whale River (0 = 6 6 . 6 ° , e - 3 4 7 . 4 ° ) , M c G l l l (<b = 5 7 . 0 ° , 0 - 3 5 4 . 3 ° ) , and Ralston (0 = 5 3 . 0 ° , 9 = 3 0 5 . 5 ° ) a l s o i n d i c a t e that i n some instances the period of Pc3 may be observed to be longer at Great Whale, while i n other instances the period of Pc3 i s the same f o r a l l s t a t i o n s . On some occasions the period of Pc's i n the high l a t i t u d e has even been found to be shorter than that observed i n the m i d - l a t i t u d e . We s h a l l describe these r e s u l t s i n S e c t i o n V . 2 as a prelude to f u r t h e r i n v e s t i g a t i o n to be made i n the l a t e r s e c t i o n s . I t has been recognised that 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 obtained from experimental observations. The l a c k of s u f f i c i e n t high q u a l i t y data may be taken as one of 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 that unless data obtained from d i f f e r e n t s t a t i o n s are recorded simultaneously with i d e n t i c a l equipment and with standardized techniques and c a l i b r a t i o n s , i t would be very d i f f i c u l t f o r one to compare these data i n an exact manner. Because of the 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 researchers have to r e s o r t to 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 to research i n the f i e l d . S t a t i s t i c a l analyses undoubtedly have y i e l d e d much informa-t i o n of various types 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 to be very misleading, p a r t i c u l a r l y when more than one parameter i s 113 involved i n the study. The second major cause of the apparent i n c o n s i s t e n c y of the o b s e r v a t i o n a l r e s u l t s i s the present l a c k of 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 r e l a t e d t o p i c s w i t h i n the same f i e l d . I t should be noted t h a t , even i n the comparison of simultaneous events, c o r r e l a t i o n s may not always be meaningful. In the study of the l a t i t u d e dependence of p u l s a t i o n frequency, f o r instance, comparison of any s t a t i s t i c a l l y obtained mean periods or frequencies may be very misleading indeed where no account has been taken of 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 . Thus the l a c k of p r e c i s e knowledge of the d i u r n a l behaviour or K - dependence of Pc3 at any s i n g l e s t a t i o n would also P hamper research on i t s l a t i t u d e dependence. The three main s t a t i o n s that we have chosen f o r comparison are s i t u a t e d i n such a p o s i t i o n that Great Whale River and M c G i l l l i e c l o s e l y on the same geomagnetic meridian whereas Ralston and M c G i l l are at about the same geomagnetic l a t i t u d e . T h e . t e l l u r i c sonagrams published i n High L a t i t u d e Geophysical Data by the Geophysical I n s t i t u t e , College, Alaska ((J) = 64.65°N, Q = 256.56°E) over a period from January to March 1967 have a l s o been used f o r comparison. Our present emphasis i s on the d e t a i l e d study of t y p i c a l events select e d according to the c l a s s i f i c a t i o n scheme proposed i n Chapter I I I . Observations made at Ralston are taken as a base f o r comparison with other s t a t i o n s 114 because of the high quality of i t s tape recorded data. Examples displayed for i l l u s t r a t i v e purposes are so selected that only data available from the maximum possible number of stations are used. Unfortunately only very few tape recorded data from Great Whale River are of s u f f i c i e n t l y low noise to signal r a t i o , and no magnetic tape recorded data are available from McGill, so except f o r the few available tape recorded data from Great Whale River and College, Alaska, comparison can be made only on chart records. In Section V .4 the la t i t u d e dependence of P c 3 frequency w i l l be studied In the l i g h t of the recently acquired knowledge on the diurnal v a r i a t i o n of frequency at Ralston (Chapter III) and at Great Whale River (Section V . 3 ) , and also on the K p-dependence of Pc3 reported i n the l a s t chapter. I t has been found that some of the apparent inconsistency i n the previous as well as i n the present observational r e s u l t s may be resolved In the present study under the new perspective. This i s to be summarized i n Section V .6 . In Section V . 5 , conjugacy of P c 3 of both the high and mid-latitude p a i r (Great Whale-Byrd and McGill-Elghts respectively) has been studied. Preliminary r e s u l t s indicate that Pc3 i s conjugate i n general except under very disturbed magnetic conditions. 115 V.2 LATITUDE DEPENDENCE OF Pc3 FREQUENCY -P r e l i m i n a r y Observations on Rapid-Run Magnetograms S c r u t i n y of rapid-run magnetograms ( 3 / 4 i n c h per minute recording speed) from Great Whale R i v e r , Ralston and M c G i l l has i n d i c a t e d that under d i f f e r e n t c o n d i t i o n s the frequency of the Pc type of magnetic p u l s a t i o n at the high l a t i t u d e s t a t i o n may be found to be higher than, or lower than, or the same as, the frequency of the p u l s a t i o n a c t i v i t y observed at the m i d - l a t i t u d e s t a t i o n s . Each of these cases has been reported by other researchers from other o b s e r v a t o r i e s . However, i t has been observed at the three Canadian s t a t i o n s that c e r t a i n r e g u l a r i t i e s could be found governing the existence of each of the d i f f e r e n t behaviours. Some of the p r e l i m i n a r y r e s u l t s obtained by study of r a p i d -run magnetograms simultaneously recorded at d i f f e r e n t s t a t i o n s i s to be reported 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 to deeper i n v e s t i g a t i o n to be presented i n the fu t u r e s e c t i o n s . No c l e a r l a t i t u d e dependence of Pc3 frequency has been observed under very quiet magnetic c o n d i t i o n s ; the frequency of Pc3 i s comparable at Great Whale, M c G i l l as w e l l as at Rals t o n . In F i g . V.2a, the constancy of Pc3 frequency with respect to d i f f e r e n t l a t i t u d e s i s i l l u s t r a t e d where peak to peak c o r r e l a t i o n i s observed f o r that p a r t i c u -l a r Pc3 event simultaneously o c c u r r i n g at Great Whale, 1 1 6 Ralston and M c G i l l under very quiet magnetic c o n d i t i o n s (Kp - 0 + ) . As the magnetic c o n d i t i o n becomes more di s t u r b e d , the l a t i t u d e dependence of Pc3 frequency 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 afternoon, but the Pc3 frequency remains comparable between the two s t a t i o n s i n the morning. An example given i n F i g . V . 2 b shows a c l e a r l a t i t u d e dependence of frequency of P c 3 where the event observed at Great Whale ( 2 0 — » 2 5 mHz) i s of much lower frequency than that observed at M c G i l l ( 3 5 —* 4 0 mHz). I t I s very i n t e r e s t i n g to note that at Ralston before 1 8 4 3 U.T. and a f t e r l o 4 6 U.T., the Pc3 i s observed with approximately 2 0 — 2 5 mHz i n frequency comparable to Great Whale, whereas i n the i n t e r v a l between 1 8 4 3 U.T. and 1 8 4 6 U.T. the frequency of Pc3 i s comparable to that at M c G i l l rather than at Great Whale. In f a c t , even peak to peak c o r r e l a t i o n could 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 Pc3 frequency over each of these s t a t i o n s would s u r e l y suggest that the mean frequency of Pc3 decreases as l a t i t u d e i n c r e a s e s . I t i s the author's opinion that such a c o n c l u s i o n i s , to say the l e a s t , very misleading. On the other hand, i f the model postulated i n Chapter I I I and r e i n f o r c e d by Chapter IV that there e x i s t s eigen o s c i l l a t i o n i n the P c 3 frequency range i n both the plasmatrough and the plasmasphere i s to be accepted, the outcome of the observation 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 only l o g i c a l that i f Great Whale 1 1 7 i s i n the plasmatrough while McGill i s i n the plasmasphere, the frequency of Pc3 observed at the two stations would be d i f f e r e n t , being higher at McGill i n this p a r t i c u l a r case. 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 Ralston that Ralston may at one time be found inside the plasmapause and at other time outside the plas-mapause i n the plasmatrough, then the frequency of Pc3 observed at Ralston would surely be changed accordingly. This i s what has been observed i n Fig . V . 2 b . To provide further support f o r our postulation that eigen o s c i l l a t i o n may exist i n the plasmatrough, the following experimental observation i s considered. There i s another class of micropulsation known as Pel with frequency range from 0 .2 Hz to 5 Hz. These micro-pulsations, appear i n polar regions (including the auroral zones) as well as i n the mid- and low-latitudes. In mid-and low-latitudes they are more l i k e l y to appear during night time than during the day. This type of a c t i v i t y i s known to be a hydromagnetic wave that originates i n the plasmatrough several to fourteen earth's r a d i i distant and Is propagated to one (or more) l i m i t e d area(s) i n the polar region along magnetic l i n e s of force (Jacobs and Watanabe, 1964$ Obayashi, 1964; Wentworth,1966). It 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 this type of Pel and the P c 3 , whose in t e n s i t y i s also greater than at mid l a t i t u d e stations, then one could i n f e r that the P c 3 118 o b s e r v e d 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 p l a s m a t r o u g h . 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 h e l i c o r d e r c h a r t s r u n n i n g a t a speed o f 3 cm/min o f t e n appear i n bu n d l e s ( p e a r l s ) . F u r t h e r m o r e , the envelope o f the P e l o b s e r v e d i n the daytime a t Great Whale i s o f t e n found t o be o f 20-30 sec 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 p a r t i c u l a r t y p e o f 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 the same s t a t i o n i s e x t r e m e l y good ( F i g . V . 2 c ) . T h i s cannot 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 than the b e a t i n g f r e q u e n c y 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 sonagram ( w h i c h has a bandwidth.M" = 0.2 Hz i . e . T B e a t ~ s e c ) . T h i s may suggest t h a t Pc3 i s a t l e a s t 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 o f the a m p l i t u d e o f P e l . I f t h i s i s i n d e e d the c a s e , the Pc3 observed must a l s o o r i g i n a t e o u t s i d e the knee boundary. i.82 r AT 0.5 Hz GW MG 1.38 r AT 0.5 HE 0.19^ AT 0.5 H z o.i i r AT 0.5 Hx J I I 1 I I I |_ Jj L -1845 1850 U.T. FIGV.2b X b , February 17, 1967 K p = 3 0 ro O GREAT WHALE, AUGUST 22. 1966 Pc I Envelope GREAT WHALE X , AUGUST 22. 1966 FIG V. 2c Pc3 Modulated Pc 1 t - 1 122 V . 3 DIURNAL VARI A T I O N OF Pc3 AT A HIGH LATITUDE STATION  - GREAT WHALE RIVER (GEOMAGNETIC (ft = 66.6°, L = 7 . 5 ) D u r i n g m o d e r a t e t o m i l d l y d i s t u r b e d c o n d i t i o n s (K = 2 t o 4 ) , t h e d i u r n a l v a r i a t i o n o f m i c r o p u l s a t i o n . a c t i v i t y may be r o u g h l y c l a s s i f i e d i n t o f o u r r e g i o n s d i v i d i n g t h e w h o l e 24 h o u r s . The p a t t e r n o f a c t i v i t y on a t y p i c a l d a y h a s b e e n d r a w n i n F i g . V . 3 a w h i c h i s s i m i l a r t o t h e one g i v e n b y J a c o b s and W r i g h t (1965) f o r B y r d S t a t i o n . F r o m 17Q0 L.T. t o 2000 L.T. ( i . e . 2200 U.T. t o 0100 U.T.) i s t h e d u s k r e g i o n . T h i s i s t h e r e g i o n where p o s i t i v e b a y i s u s u a l l y v e r y a c t i v e . I t i s e x t r e m e l y i n t e r e s t i n g t o n o t e t h a t f o r e v e r y e v e n t o f p o s i t i v e b a y o b s e r v e d t h e r e h a s a l w a y s b e e n r e g u l a r m i c r o p u l s a t i o n o f 10 t o 20 s e c p e r i o d ( P c 2 and Pc3) a s s o c i a t e d w i t h i t . Pc5 a l s o i s v e r y o f t e n o b s e r v e d s i m u l t a n e o u s l y . P o s i t i v e b a y s o c c u r v e r y o f t e n i n t h e a u r o r a l z o n e ; f r o m d a t a s t u d i e d i n a t e n d a y p e r i o d i n S e p t e m b e r 19&5 a l o n e , t h e r e a r e 7 c a s e s o f s u c h e v e n t s b e i n g o b s e r v e d . One t y p i c a l e x a m p l e o f t h i s d u s k t y p e P c 2 - 3 a s s o c i a t i o n w i t h p o s i t i v e b a y i s shown i n F i g . V . 3 b . I n t h e u p p e r p o r t i o n o f t h e d i a g r a m t h e r e i s a p a r t o f a h i g h s p e e d r e c o r d e d m agnetogram s h o w i n g a t y p i c a l P c 2 - 3 e v e n t n e a r d u s k , and t h e r e i s a L a C o u r t y p e o f rnagnetogram o f t h e same e v e n t shown i n t h e l o w e r p o r t i o n w h i c h i s r e c o r d e d a t r e l a t i v e l y s l o w e r s p e e d and h a s much p o o r e r f r e q u e n c y r e s p o n s e . The 1 2 3 P c 2 - 3 e v e n t shown t a k e s p l a c e f i r s t a r o u n d 2208 U.T. and i t i s i n t e r e s t i n g t o n o t e t h a t t h i s i s t h e v e r y moment t h a t a p o s i t i v e b a y b e g i n s t o be o b s e r v a b l e . A n o t h e r f e a t u r e t h a t s h o u l d be n o t e d i s t h a t a f t e r 2240 U.T., t h e p e r i o d o f t h e same e v e n t b e g i n s t o d e c r e a s e c o n t i n u o u s l y . T h i s r e m i n d s u s o f a n o t h e r t y p e o f g e o m a g n e t i c p u l s a t i o n c a l l e d IPDP w h i c h when o b s e r v e d , u s u a l l y o c c u r s a r o u n d t h i s p a r t i c u l a r l o c a l t i m e and i s a l w a y s i d e n t i f i e d b y i t s d e c r e a s i n g p e r i o d . However, IPDP i s u s u a l l y o f h i g h e r f r e q u e n c y . I n t h e a b s e n c e o f p o s i t i v e b a y , t h e d u s k r e g i o n i s u s u a l l y q u i e t . The o n l y a c t i v i t y t h a t may s t i l l be o b s e r v e d i s Pc5 w h i c h h a s n o t a p p e a r e d i n F i g . V.3b. The s e c o n d r e g i o n e x t e n d s f r o m 2100 L.T. t o 0100 L.T. (0200 U.T. t o 0600 U . T . ) . T h i s i s t h e r e g i o n where p u l s a t i o n o f t h e i m p u l s i v e t y p e u s u a l l y o c c u r s . A t y p i c a l e x a m p l e o f a P 1 2 e v e n t i s p r e s e n t e d i n F i g . V . 3 d . As may be s e e n i n t h i s e x a m p l e , P c 2 and Pc3 a r e o f t e n f o u n d s u p e r i m p o s e d on t h e s e i m p u l s i v e r n i c r o p u l s a t l o n e v e n t s . The c o n d i t i o n i s g e n e r a l l y q u i e t i n t h e a b s e n c e o f t h e s e i m p u l s i v e e v e n t s a l t h o u g h t r a c e s o f s h o r t e r p e r i o d ( ^  10 s e c ) p u l s a t i o n a c t i v i t y may s o m e t i m e s be I d e n t i f i e d . The e a r l y m o r n i n g r e g i o n b e f o r e o r n e a r dawn (C100 L.T. - 0600 L.T. o r 0600 U.T. - 1100 U.T.) i s a r e g i o n o f t e n i n v a d e d b y n e g a t i v e bays. S i m i l a r t o t h e f i r s t r e g i o n m e n t i o n e d a b o v e , t h e r e have a l s o b e e n P c 2 and P c 3 e v e n t s 124 associated with every negative bay that we observed i n t h i s region. The amplitude of the bay associated Pc2 - 3 has maximum at the recovery stage of the bay then e v e n t u a l l y d i e s down towards dawn. Before or at 0600 L.T., a quiet 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 the onset of day time Pc3 a c t i v i t y . One of the events observed i s i l l u s t r a t e d i n F i g . V.3c where both negative bay and Pc2 and Pc3 (10 —» 20 sec) p u l s a t i o n events occurs simultaneously around O650 U.T. P u l s a t i o n of longer period may o c c a s i o n a l l y be present i n the same event which by I t s e l f i s o f t e n f l u c t u a t i n g i n per i o d . Notice also that the 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 only a f t e r the bay enters i t s recovery phase at around 0725 U.T. and then d i e s down toward dawn. In the absence of bay a c t i v i t y , a longer period Pc3 wi t h smaller amplitude i s u s u a l l y detected with or without Pc5 occurrence. The day region (0600 L.T. to 1700 L.T.) i s very a c t i v e i n continuous p u l s a t i o n events with frequency ranging from 25 Hz to 70 Hz. The frequency i s u s u a l l y at i t s highest j u s t a f t e r dawn and at i t s lowest In the afternoon. Such a change i n frequency does not seem to take place continuously. The daytime Pc3 appears to be very s e n s i t i v e to the change in•the dimension of the 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 before and around l o c a l noon. Pc3 events are 125 g e n e r a l l y a l i t t l e more reg u l a r between 0700 L.T. and 0900 L.T. when there seems to 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 . A secondary maximum i s o f t e n found around 1400 L.T. or '1500 L.T. In f a c t , cases of very r e g u l a r Pc2 of 10 to 20 sec period have been found on many occasions i n the afternoon (1300 to 1600 L.T.) instead of longer period P c 1 s (the August 19, 1966 event i s one of the t y p i c a l examples). Also, i t does not seem that there i s a d e f i n i t e boundary between Pc2 and Pc3 as suggested by the IAGA committee, 1 9 6 4 . In general, the frequency of Pc2 - 3 i n the high l a t i t u d e s f l u c t u a t e s throughout the day except under very quiet c o n d i t i o n s . At times when the geomagnetic disturbance i s found to be at i t s minimum ( K p = 0 - > 1 ) , 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 (0300 to 1700 L.T.). D i u r n a l v a r i a t i o n i n frequency does not seem to be very s i g n i f i c a n t . The i n t e n s i t y of these Pc3 - 4 p u l s a t i o n s appears to be at i t s maximum i n the l o c a l morning and then decreases towards afternoon. A t y p i c a l rjver:t he2 been reproduced i n ? i g . 7 . 3 e where ne a r l y peek to peak c o r r e l a t i o n has been shown to occur between highl-and m i d - l a t i t u d e s t a t i o n s f o r these types of Pc3 - 4 a c t i v i t i e s . in.'i.v I :io IK: lY ' U i u l to occur i n the afternoon under extremely quiet 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 occurs at a l e s s frequent r a t e . The impulsive type of P i 2 m i c r o p u l s a t i o n 126 usually observed around midnight also occurs l e s s frequently. Conditions are generally very quiet from dusk to afte r mid-night although less regular pulsation i n the Pc2 - 3 frequency range may s t i l l be detected i n association with bay. Unfortunately, good data obtained during stormy conditions are r a r e l y available at Great Whale River, as they are usually recorded o f f scale. However, Information extracted from the available data Indicates that during stormy conditions, the diurnal v a r i a t i o n observed under moderately disturbed conditions described above not only remains true but becomes more pronounced. The frequency of the pulsation a c t i v i t y i s much higher i n general. The night time pulsation events appear to be more violent during stormy conditions (e.g. the June 16, 1965 event). Large amplitude Pc5 may be observed continuously a l l day, p a r t i -c u l a r l y so i n the morning and i n the l a t e , afternoon. One example i s shown i n Pig. V.3f where Pc5 i s observed at both high and mid l a t i t u d e stations, a l l with Pc3 r i d e r s . FIG. V.3a DIURNAL REGIONS OF MICROPULSATION ACTIVITIES AT THE HIGH AND MID-LATITUDES FIG. V. 3b GREAT WHALE SEPT 20 1965 X FIG. V. 3c GREAT WHALE DEC 19 1965 FIG V.3b & V.3c BAY ASSOCIATED Pc3 J L I I I I I I I » I U . T . 0 9 1 5 0 ° 2 0 FIG V.3e January 21,1964 L A T I T U D E D E P E N D E N C E O F 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 provides a general g u i d e l i n e f o r research on l a t i t u d e and l o c a l time dependence of Pc3 frequency, f u r t h e r r e s u l t s of which are to be presented i n t h i s s e c t i o n . Observations made at Ralston are again chosen as a base f o r comparison with observations made at other s t a t i o n s . The multi-band s t r u c t u r e d Pc3 event observed at Ralston and described i n d e t a i l i n Section I I I . 2 has been displayed alongside the dynamic spectrum of the same event simultaneously observed at College, Alaska (Q - 64.7°). The d i s p l a y i s shown i n the lower p o r t i o n of F i g . V.4a. S i m u l t a n e i t y of occurrence and general appearance of Pc3 observed at, these two s t a t i o n s i s most remarkably demonstrated on the diagram. This i s p a r t i c u l a r l y so i n the lower frequency bands where no l a t i t u d e or l o c a l time dependence of frequency i s observed i n the day regime. The nighttime 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 at the higher l a t i t u d e . I t i s very important to note that the multi-band s t r u c t u r e so apparent at Ralston from 1700 U.T. to 210C U.T. ( i . e . around l o c a l noon) i s only b a r e l y i n existence at Colleg e . The 40 mHz band observed at Ralston becomes very weak i n the higher l a t i t u d e . This band becomes s i g n i f i c a n t at College only a f t e r 2300 U.T. From 2300 U.T. to 0100 U.T. 133 the frequency of the band Is comparable at the two s t a t i o n s . The same event recorded on magnetograms operating at chart speed of 6 inches per hour has a l s o been observed at Great Whale which i s l o c a t e d at an even higher geomagnetic l a t i t u d e than C o l l e g e . This has been compared with magneto-grams recorded w i t h the same recording speed at R a l s t o n . Part of the magnetogram (from 1400 U.T. to midnight U.T.) i s i l l u s t r a t e d i n the upper p o r t i o n of F i g . V.4a. S c a l i n g of these two magnetograms recorded at the two s t a t i o n s i n d i c a t e s that the high frequency component observed at Ralston i s c o n s t a n t l y of higher frequency than that observed at Great Whale. The highest frequency component observed at Ralston i s approximately 46 mHz o c c u r r i n g around 1700 U.T., whereas the highest frequency observed at Great Whale i s only about 25 mHz w i t h i n the same time i n t e r v a l . The frequency of the p u l s a t i o n a c t i v i t y at R a l s t o n decreases from 46 mHz at 1700 U.T. to 35 mHz at 2100 U.T. with 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 frequency of the corresponding a c t i v i t y observed at Great Whale i n the same i n t e r v a l i s obviously of much lower frequency and i t s frequency changes only 4 mHz from 25 mHz at 1700 U.T. to 21 mHz at 2100 U.T. U n l i k e R a l s t o n , s c r u t i n y of the same event observed at Great Whale shows no c l e a r evidence of m u l t i - p e r i o d i c i t y i n the Pc3 frequency 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 place at both Ralston and Great Whale, Note, f o r example, that the 134 amplitude of the wave packet o c c u r r i n g around 1815 U.T. at Great Whale i s approximately 3.15 7 (at 25 mHz) whereas the corresponding wave packet observed at Ralston i s only 1.7 7 i n amplitude (at 40 mHz). Maximum i n t e n s i t y occurs around 1900 U.T. at both s t a t i o n s and diminishes from then on to reach i t s lowest value at approximately 2200 U.T. The b e a u t i f u l Pc3 event of approximately 30 mHz i n frequency that appears a f t e r 2300 U.T. at Ralston i s very i n t e r e s t i n g because i t i s of much greater i n t e n s i t y ( 1.6 7) than the corresponding event observed at Great Whale ( - 0.5 7). This may be p a r t l y due to the l o c a l time dependence. Another example s i m i l a r to the one described above i s shown i n F i g . V . 4 b . In the lower p o r t i o n of the diagram, sonagrams produced from data recorded at College and Ralston have been d i s p l a y e d f o r comparison. The higher frequency component (35 mHz) observed at Ralston i s again found to be much stronger i n s i g n a l strength than the corresponding component observed at College. The other frequency components are comparable i n frequency, time of occurrence and i n s i g n a l strength between the 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 al s o evident at Great Whale and Ralston. In F i g . V.4c, magnetograms from Great Whale (the upper magnetogram) and from Ralston have been shown side by side f o r comparison. This p a r t i c u l a r event has already been 135 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 . 3 where t h e d y n a m i c s p e c t r u m o f t h e same e v e n t i s d i s p l a y e d i n F i g . I I I . 3 a f o r R a l s t o n . However, a s i t h a s b e e n c l e a r l y d e m o n s t r a t e d i n F i g . V . 3 c , Pc3 b e h a v e s d i f f e r e n t l y a t G r e a t W h a l e . C l o s e c o r r e l a t i o n b e t w e e n h i g h and m i d - l a t i t u d e Pc3 i s f o u n d o n l y i n t h e m o r n i n g (1200 U.T. t o 1830 U.T. i n t h e O c t o b e r 18 e v e n t s h o w n ) . The f r e q u e n c y , on t h e o t h e r h a n d , i s s l i g h t l y h i g h e r a t t h e m i d - l a t i t u d e s . The f r e q u e n c y a s w e l l a s t h e a m p l i t u d e o f t h e Pc3 a c t i v i t y d e c r e a s e f r o m 1300 U.T. (0600 L.T. a t R a l s t o n ) t o a r o u n d 1900 U.T. a t b o t h G r e a t Whale and R a l s t o n . B u t t h e r a t e o f d e c r e a s e i n b o t h a m p l i t u d e and f r e q u e n c y i s much g r e a t e r a t G r e a t Whale t h a n a t R a l s t o n . The 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 , w h i c h i s o f h i g h e r f r e q u e n c y (40 mHz), i s v e r y a c t i v e a t t h e m i d -l a t i t u d e R a l s t o n s t a t i o n . T h i s i s c o n t r a r y t o what h a s b e e n o b s e r v e d a t G r e a t Whale where Pc3 a c t i v i t y i s f o u n d t o be a t i t s minimum. The p u l s a t i o n a c t i v i t y o b s e r v e d a t G r e a t Whale i n t h e a f t e r n o o n i s u s u a l l y o f s m a l l e r a m p l i t u d e and i s l e s s r e g u l a r . However, v e r y r e g u l a r P c 2 o f 10 s e c t o 20 s e c p e r i o d s may o f t e n be f o u n d t o o c c u r i n t h e a f t e r n o o n , w h i c h h a v e no c o u n t e r p a r t i n t h e mid l a t i t u d e s ( s e e F i g . V . 4 d ) . The 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 o f Pc3 f r e q u e n c y o b s e r v e d u s u a l l y a t R a l s t o n u n d e r m o d e r a t e l y t o v e r y q u i e t c o n d i t i o n s h a s a c o u n t e r p a r t a t t h e h i g h e r l a t i t u d e s . I n F i g . V.4e, an e v e n t t a k i n g p l a c e on F e b r u a r y 2o, 1967 and o b s e r v e d 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 C o l l e g e h a s b e e n d i s p l a y e d f o r c o m p a r i s o n . No l a t i t u d e 136 dependence of Pc3 f r e q u e n c y has been observed between the two s t a t i o n s . The mean f r e q u e n c y of Pc-3 e v e n t s I s found t o be the same a t both s t a t i o n s . The wide band of a c t i v i t y ( P i 2 ) i n v a d i n g c o l l e g e at 1 2 0 0 U.T. and loOO U.T. ( i . e . 0 2 0 0 L.T. and OoOO L.T. at C o l l e g e ) was not observed at R a l s t o n . T h i s may be due to l o c a l time dependence. Because R a l s t o n i s t h r e e hours i n time ahead of C o l l e g e , i t may not o c c u r at R a l s t o n where i t i s a l r e a d y e a r l y i n the day regime. Another i n t e r e s t i n g f e a t u r e t o be noted on Fig.V.4e i s the t r a c e of Pc4 a c t i v i t y (10 milz) observed at C o l l e g e . No d i s t i n c t Pc4 has been observed at R a l s t o n . The c l o s e correspondence of the f r e q u e n c y of the Pc3 a c t i v i t y between R a l s t o n and C o l l e g e under m o d e r a t e l y q u i e t c o n d i t i o n s c o u l d not be found at Great Whale which i s of even h i g h e r l a t i t u d e and i s two hours i n l o c a l time ahead o f R a l s t o n . The two sonagrams o b t a i n e d from d a t a r e c o r d e d at Great Whale and R a l s t o n are shown i n F i g . V . 4 f c o v e r i n g two days i n time i n t e r v a l (Feb. 26 and 27, 1 9 6 7 ) , A l a t i t u d e dependence of mean f r e q u e n c y of Pc3 i s found t o be c o n s i d e r a b l e between the two s t a t i o n s . At Great Whale, the s e p a r a t i o n between the P c 3 and Pc4 bands i s not at a l l c l e a r (the e x i s t e n c e of which i s d o u b t f u l at the h i g h l a t i t u d e s ) . An average over the two bands would r e s u l t i n a lower v a l u e of the mean p u l s a t i o n f r e q u e n c y . Thus the mean f r e q u e n c y observed at Great Whale i s much lower t h a n 137 that observed at Ralston. Also, the amplitude of Pc3 at the high l a t i t u d e s t a t i o n appears to be a maximum e a r l y i n the morning (OoOO L.T.), co n t r a r y to the noon maximum observed at both Ralston and College 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 Pc3 frequency. The l o c a l time dependence as w e l l as the l a t i t u d e dependence have a profound e f f e c t on the Pc3 c u t - o f f . The Pc3 range of m i c r o p u l s a t i o n cuts o f f at around 1300 U.T. February 26, 1967 at Great Whale and n e a r l y terminates at midnight U.T. at Ralston ( F i g . V . 4 f ) , while 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 February 27, 1967 at College. 138 FIG.V.4a Multi-Band Structured Pt 3 139 13 FEB V 80 -60 FIG.V.4b Multi-Band Structured Pc3 140 G W - / 13 15 OCT £9,67 \ • • V " ' " \ \ ' ' V ' \ ' " A C | C F (9,67 \ ' ' \ " • V 29 §.717 1.1*7 U . T . -6* w - * n 4AA- LATITUDE DEPENDENCE OF r l U . V . 4 C ' OUT 1 o v i 3 o 7 NORMAL TYPE OF Pc3 GW MG 1.45V at0.5Hz 0.65 r at0.5Hz 0.32 V at 0.5Hz 2.72r at0.5Hz 2100 2105 2110 FIG V.4d September 19 1965 Pc3 AT TIE MID-LATITUDES 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 L a t i t u d e D e p e n d e n c e o f P c 3 V . 5 C O N J U G A C Y OF Pc3 AT HIGH AND MIDDLE LATITUDES C o n j u g a t e s t u d i e s o f t h e c o n t i n u o u s p u l s a t i o n a r e made i n t h e p r e s e n t r e s e a r c h m a i n l y a t t h e p a i r o f s t a t i o n s B y r d , A n t a r c t i c a and G r e a t Whale R i v e r , C a n a d a . O n l y tvio weeks' d a t a i n one component ( t o t a l f i e l d F ) a r e a v a i l a b l e f r o m E i g h t s , A n t a r c t i c a (a) = 6 3 .8°, 0 « 3 5 5 . 3 ° g e o m a g n e t i c ) . I t i s f o u n d h o w e v e r t h a t i n most c a s e s u n d e r s t u d y p u l s a t i o n a c t i v i t y on t h e X o r Y f i e l d component r e c o r d e d a t M c G i l l a r e s i m i l a r i n a p p e a r a n c e t o t h e s i g n a l s a t F i g h t s r e c o r d e d on t h e t o t a l f i e l d c o m p o n e n t . M c G i l l and E i g h t s a r e n e a r c o n j u g a t e p a i r o f s t a t i o n s i n t h e m i d l a t i t u d e s . D u r i n g e x t r e m e l y q u i e t c o n d i t i o n s (K - 0 —> 1) l o n g e r p e r i o d Pc3's ( s o m e t i m e s Pc4) a r e o b s e r v e d a t b o t h 3yrd and G r e a t W h a l e . T h i s t y p e o f a c t i v i t y shows v e r y good p e a k t o p e a k c o n j u g a c y and i s o b s e r v e d m a i n l y when t h e s t a t i o n s a r e on t h e d a y l i g h t s i d e o f t h e e a r t h . T h r e e e x a m p l e s a r e shown i n F i g . V . 5 a where p e a k t o p e a k c o n j u g a c y i s o b s e r v e d f o r t h e v e r y r e g u l a r waves, b o t h i n t h e m o r n i n g and i n t h e a f t e r n o o n . O n l y t h e n e a r l y s i n u s o i d a l waves a r e 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 . U n f o r t u n a t e l y , no d a t a have b e e n a v a i l a b l e f r o m S i g h t s u n d e r v e r y q u i e t c o n d i t i o n s . B u t g o o d , i f n o t b e t t e r , c o n j u g a c y o f Pc3 i s t o be e x p e c t e d f o r t h e m i d - l a t i t u d e p a i r s . I n f a c t , e v e n when t h e m a g n e t i c c o n d i t i o n becomes m o d e r a t e l y d i s t u r b e d , • but n o t v i o l e n t l y d i s t u r b e d , t h e c o n j u g a c y o f ? c 3 r e m a i n s good i n t h e m i d -l a t i t u d e s . One e x a m p l e o f s u c h i s shown a t t h e b o t t o m o f F i g . V.5a where peak t o p e a k c o n j u g a c y h a s b e e n o b s e r v e d f o r t h e m i d - l a t i t u d e p a i r s . C o n j u g a c y of t h e dawn and d u s k t y p e ?c2,3 o b s e r v e d a t t h e 3 y r d - G r e a t " h a l e p a i r i s a p p a r e n t i n o v e r a l l a c t i v i t y O c c a s i o n a l l y p e a k t o pe a k c o r r e s p o n d e n c e i s s e e n , however. An e x a m p l e i s shown on F i g . V.fjb f o r e a c h o f t h e s e two 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 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 = •'-!-), Pc3 a c t i v i t y o b s e r v e d a t t h e m i d -l a t i t u d e p a i r d i s p l a y s more p e a k t o p e a k c o r r e s p o n d e n c e t h a n a t t h e h i g h - l a t i t u d e p a i r . The S e p t e m b e r 16, 1965 e v e n t shewn i n F i g . V . 5 c i s one s u c h e x a m p l e . I n g e n e r a l , Pc3 a c t i v i t i e s o b s e r v e d i n t h e l o c a l m o r n i n g a r e f o u n d t o 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 a f t e r n o o n . When t h e m a g n e t i c l e v e l o f d i s t u r b a n c e becomes v e r y 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 t h e G r e a t Whale-Byrd p a i r . F i g . V.5<3 shows one s u c h e x a m p l e . The Pc.3 a c t i v i t y i s c o n j u g a t e , and o c c a s i o n a l l y p e a k t o p e a k c o n j u g a t e , a r o u n d 0600 U.-T. on Ju n e 15 , 1965 when K = 1. I n t h e l o w e r p o r t i o n o f F i g . V . 5 d , i t i s s e e n t h a t c o n j u g a c y becomes p o o r e r as K i n c r e a s e s f u r t h e r £'' (0500 U.T. J u n e 16, 196.5), and f i n a l l y 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 . When K i n c r e a s e s s u b s t a n t i a l l y i n t h e a f t e r n o o n ( a r o u n d I030 U . T . ) , t h e c o n j u g a c y i s a p p a r e n t i n t h e o v e r a l l l e v e l of a c t i v i t y ; however, i n d i v i d u a l o s c i l l a t i o n s c a n n o t n e c e s s a r i l y be c o r r e l a t e d . 1 4 6 GW 1.96 7 at 0 . 5 H2 0.79 r at 0 . 5 Hs J L J I l_ J I I L 1520 1525 December 14 1965 Kp = 1-GW l.Q?. 7 at 0 .5 Ks 0.25 7 at 0 . 5 Hz GW ' ' ' J 1_ I L J ' I 1220 1225 December 17 1965 Kp = 0+ - i 1 1 u 1804 1810 1815 June 24 1965 Kp<=1+ j i_ 1.52 7 at 0 .5 Ks 2.31 7 at 0 .5 H 3 MG r 1 0 .32 7 a t 0 . 5 H' 0 . 0 4 y at 0 . 5 Hz _1 r_ J I I L U. T. 1035 1040 September 19 1965 Kp = 3-1043 FIG V5a CONJUGACY OF Pc3 0810 0815 U.T. September 20 1965 FIG V.5b CONJUGACY OF DAWN AND DUSK TYPE Pc2,3 G W - Y L 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 J I L J I I L 1 5 5 0 1 5 5 5 U . T . F I G V *r Q p n t I R f a c e C O N J U G A C Y O F P C 3 A T riva v .oc oept T O , I y o o H I G H A N D M I D L A T I T U D E S 150 V.6 .DISCUSSIONS In Chapter I I I , the existence of eigen o s c i l l a t i o n s ' of modified A l f v e n mode outside the plasmapause i n the plasmatrough has been p o s t u l a t e d , i n a d d i t i o n to the eigen o s c i l l a t i o n already widely b e l i e v e d to e x i s t i n s i d e the plasmasphere. This model has been used to e x p l a i n the existence of d i f f e r e n t types of d i u r n a l v a r i a t i o n of Pc3 frequency experimentally observed at Rals t o n . The same model has been used a l s o to i n t e r p r e t r e s u l t s on K P dependence of Pc3 frequency studied i n Chapter IV. I t has been found that experimental r e s u l t s obtained so f a r agree with 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 the proposed model. In t h i s s e c t i o n , the same model w i l l again be employed to In t e r p r e t r e s u l t s reported i n the e a r l i e r s e c t i o n s . The fjj_ band of Pc3 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 considered to be a high-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 the f_ band of Pc3 i s considered to o r i g i n a t e i n 3 the plasmasphere bounded by the plasmapause. Occurrence of the multi-band s t r u c t u r e d Pc3 at Ralston has been thought of as a boundary e f f e c t which takes place when Ralston Is s i t u a t e d c l o s e to the plasmapause. I f t h i s i s indeed the case, s t a t i o n s of higher l a t i t u d e than Ralston should observe Pc3 that has frequency comparable to the f ^ band observed simultaneously at Ralston under moderately d i s t u r b e d 151 c o n d i t i o n s . On the other hand, the frequency of Pc3 events observed at s t a t i o n s of lower l a t i t u d e than Ralston would be dominated by the f ^ band. Close examination of magnetograms simultaneously obtained from R a l s t o n , College and Great Whale have i n d i c a t e d that Pc3 i n the higher l a t i t u d e s indeed behaves as p r e d i c t e d by the proposed model. The two examples given i n F i g . V.4a and F i g . V.4b are only two of many examples that could show the f ^ band to be very weak i n the higher l a t i t u d e s before noon. The lower frequency component ( <^> 25 to 30 mHz) of Pc3 has been observed simultaneously at both high and mid l a t i t u d e s t a t i o n s with comparable i n t e n s i t y . This obser-v a t i o n a l f a c t could not be i n t e r p r e t e d c o r r e c t l y without a p r i o r knowledge of the simultaneous behaviour of t h i s p a r t i c u l a r frequency band at the lower l a t i t u d e s . The event observed simultaneously at R a l s t o n and College i n the afternoon i s of p a r t i c u l a r i n t e r e s t . This may be taken as f u r t h e r evidence of the east-west asymmetry of the plasmapause c o n f i g u r a t i o n . Under moderately d i s t u r b e d c o n d i t i o n s , as i n the February 11, 1967 event shown (Fig.V.4a), Ralston u s u a l l y i s very c l o s e to the plasmapause. College, being at a higher geomagnetic l a t i t u d e than Ralston, i s u s u a l l y w e l l outside the plasmapause. This i s p a r t i c u l a r l y so i n the morning when the geocentric distance of the plasmapause i s at i t s minimum (Carpenter, 1966). As the geocentric distance of the plasmapause increases to i t s 152 maximum l a t e r i n the afternoon, both Ralston and College may be found i n s i d e the plasmapause, i n which case the f ^ band of Pc3 would be observed at Ralston as w e l l as at College i n s t e a d of the other Pc3 band that was observed e a r l i e r i n the day. This i s the phenomenon responsible f o r the occurrence of the event simultaneously observed at Ralston and College around midnight U.T. February 11, 1967 shown i n F i g . V.4a. The same event was observed only vaguely at Great Whale because the l a t i t u d e i s so high that no boundary c r o s s i n g took place. Unfortunately, no data simultaneously recorded at a 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 f o r comparison. However, various workers have reported r e s u l t s of t h e i r observations, both i n the low and i n the m i d - l a t i t u d e s t a t i o n s . These r e s u l t s have been tabulated i n Table V . l to show the mean frequency of Pc3 observed'by d i f f e r e n t authors at d i f f e r e n t l a t i t u d e s . I t may be seen from Table V . l that the mean frequency of Pc3 observed by most workers at geomagnetic l a t i t u d e s lower than 60° i s around 30 to 45 mHz. A l l o w i n g f o r the d i f f e r e n t s c a l i n g methods used by d i f f e r e n t authors, and also bearing i n mind the l i m i t a t i o n of the s t a t i s t i c a l methods employed, the r e s u l t i s i n very good agreement with the f ^ band of Pc3 that has been observed at Ralston. This i s c o n s i s t e n t with our s p e c u l a t i o n that 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 from the Inside of the plasmasphere. 153 In Chapter I I I , the morning type of Pc3 observed at Ralston on October 18, 1967 under moderately d i s t u r b e d c o n d i t i o n s has been speculated to be a h i g h - l a t i t u d e phenomenon t a k i n g place when Ralston i s i n the plasmatrough, whereas the afternoon type of Pc3 o c c u r r i n g on the same day i s considered to o r i g i n a t e i n s i d e the plasmasphere and i s observed only a f t e r boundary c r o s s i n g took place e a r l y i n the afternoon. This i s c o n s i s t e n t with r e s u l t s reported i n S e c t i o n V.4 where the same event recorded simultaneously on c h a r t s at Ralston and Great Whale has been compared. I t was found that close c o r r e l a t i o n between Pc3 observed at Ralston and that observed at Great Whale e x i s t s only i n the morning when the i n t e n s i t y of the Pc3 a c t i v i t y i s much greater at Great Whale than at R a l s t o n . This i s a c l e a r evidence t h a t the morning type of Pc3 observed at Ralston i s a h i g h - l a t i t u d e phenomenon. The afternoon type of Pc3 observed at Ralston i n the afternoon, however, has no counterpart i n the high l a t i t u d e s . This again i s c o n s i s t e n t with the s p e c u l a t i o n that the afternoon type of Pc3 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. Since under quiet 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 to 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 Ralston and that observed at C o l l e g e , 154 as both of them are expected to be found i n s i d e the plasmapause. When the c o n d i t i o n s become extremely q u i e t , then the Pc3 at Great Whale too would have the same frequency and the same d i u r n a l behaviour as at the other s t a t i o n s i n the lower l a t i t u d e s . • The l o c a l time dependence of the Pc3 c u t - o f f may also be explained a f t e r the asymmetry of the plasmapause c o n f i g u r a t i o n has been taken i n t o account. The boundary c r o s s i n g should take place three hours e a r l i e r at Ralston than at Co l l e g e . TABLE V. 1 LATITUDE DEPENDENCE OF Pc3 REPORTED BY OTHER OBSERVERS O b s e r v e r D a t a O b s e r v a t o r y Geomag. L a t . P e r i o d ( S e c ) F r e q u e : (mHz N a g a t a and F u k u n i s h i 1968 C h a r t and T a p e s K a k i o k a 26° 28 35 H i r a s a w a and N a g a t a 1966 C h a r t and T a p e s K a k i o k a 26° 28 35 K a t o and S a i t o 1959 ( D u r i n g SSC) C h a r t Onagawa 28° 20 50 Duncan 1961 C h a r t T o w n s v i l l e 29° 19 52 C a m p b e l l 1959 C h a r t B o r r e g o 39° 22 45 M a p l e 1959 C h a r t T u c s o n 40° 20 50 B e r t h o d , H a r r i s and Hope i 9 6 0 C h a r t A r i z o n a 41° 35 29 Duncan 1961 C h a r t and T a p e s A d e l a i d e 45° 23 U 0 Duncan 1961 C h a r t and T a p e s H o b a r t 52° 27 37 S c h o l t e and V e l d k a m p 1955 C h a r t W i t t e v e e n 54° 45 22 S t u a r t and U s h e r i960 C h a r t H a r t l a n d 55° 40 25 S t u a r t and U s h e r 1966 C h a r t E s k d a l e m u i r 59° 25 40 H o l m b e r g 1953 C h a r t E s k d a l e m u i r 50° 25 4 0 S t u a r t and U s h e r i960 C h a r t L e r w i c h 63° 30 33 n c y 156 CHAPTER VI  GENERAL STUDIES OF Pc4 VI. 1 INTRODUCTION Although the exact morphological p r o p e r t i e s of Pc4 i s not yet understood and there remains controversy to be resolved i n both experimental observations and the theore-t i c a l consideration's reported by various researchers since the IGY, many authors b e l i e v e that the Pc3 and Pc4 types of continuous 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 . In f a c t , i t has been common p r a c t i c e by some authors to use Pc3, 4, or simply Pc, as a u n i f y i n g n o t a t i o n to denote both the Pc3 and Pc4 types of m i c r o p u l s a t i o n s (Voelker, 1967; S i e b e r t , 1964). On the other hand, S a i t o (1966) regarded Pc4 as e s s e n t i a l l y an extension of Pc5 because Pc4 has so many morphological c h a r a c t e r i s t i c s s i m i l a r to Pc5. The p r e c i s e frequency boundary, i f there i s any, of Pc4 can be l o c a t e d only a f t e r the exact nature of i t s generating and propagating mechanism becomes understood. For t h i s purpose, the morphological p r o p e r t i e s of Pc4 must f i r s t be studied 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 of Pc4 frequency has been observed by Katp and S a i t o to behave as an i n v e r t e d U-type i n frequency (U-type i n period) w i t h minimum frequency o c c u r r i n g j u s t before the noon hour (Kato and S a i t o , 1959, 1962; S a i t o , 1962, 1964a). This i s cont r a r y to the l a t e r report of Hirasawa and Nagata (1966) and Nagata and Fukunishi (1968) who 157 observed that the Pc4 (15 mHz) band of p u l s a t i o n appears throughout almost a day, being most a c t i v e around 0900.L.T. with minimum at about 19 L.T. Using data obtained during the quiet sun p e r i o d , 1964 and 1965, Hirasawa and Nagata (1966) have shown that the frequency of the 15 mHz band increa s e s with i n c r e a s i n g geomagnetic a c t i v i t y represented by 51 Kp. Nagata and Fukunishi (1968) even derived an e m p i r i c a l r e l a t i o n expres-s i n g the l i n e a r r e l a t i o n between the maximum c e n t r a l frequency of Pc4, i . e . the mean frequency of Pc4 scaled at the time of maximum d a i l y frequency occurrence, and the average value of Kp (Kp) or the sum of Kp ( % K p ) . These f i n d i n g s have profoundly a f f e c t e d the t h e o r e t i c a l model one may use to i n t e r p r e t experimental observations reported i n the previous chapters. The l a t i t u d i n a l dependence of Pc4 amplitude has been studied by a few researchers. Kato and S a i t o (1962) reported that the maximum amplitude of Pc4 seems to be i n the a u r o r a l l a t i t u d e and there seems to be a secondary maximum e x i s t i n g i n the sub-auroral zone ((j) ^ 5 0 ° ) . E a r l i e r , Vledkamp (i960) c o l l e c t e d data from a wider d i s t r i b u t i o n of s t a t i o n s than that used by Kato and S a i t o and found that there i s a prominent maximum i n the s p a t i a l d i s t r i b u t i o n of Pc4 amplitude near the sub-auroral zones. These observations are i n agreement wi t h those of Obayashi and Jacobs . (1958) who, using about 80 days of records 15 i n s u n s p o t - m i n i m u m y e a r s f r o m 194-9 t o 1953, o b s e r v e d t h a t t h e r e i s a c o n c e n t r a t i o n o f Pc4 r a n g e o f p u l s a t i o n n e a r t h e s u b - a u r o r a l z o n e . I n t h i s c h a p t e r , we s h a l l r e p o r t p r e l i m i n a r y r e s u l t s b a s e d on a d e t a i l e d s t u d y o f t h e few l i m i t e d d a t a a v a i l a b l e i n t h e Pc4 f r e q u e n c y r a n g e . The r e c o r d s a r e m a i n l y i n t h e f o r m o f r a p i d - r u n E s t e r l i n e Angus c h a r t s . The a v a i l a b l e t a p e r e c o r d s a r e t h o s e f r o m R a l s t o n and t o a l e s s e r e x t e n t f r o m G r e a t Whale R i v e r . R a l s t o n r e c o r d s a r e u s u a l l y o f b e t t e r q u a l i t y and a r e u s e d as a b a s i s o f c o m p a r i s o n w i t h o t h e r s t a t i o n s . O n l y f r o m t h e R a l s t o n d a t a i s t h e Y f i e l d c omponent a v a i l a b l e f o r c o m p a r i s o n . The r a p i d - r u n m agnetograms r e c o r d e d i n one f i e l d c omponent P a r e a v a i l a b l e f r o m E i g h t s o v e r a p e r i o d o f two weeks i n S e p t e m b e r , 1965. T h i s e n a b l e s u s t o make a p r e l i m i n a r y i n v e s t i g a t i o n i n t o t h e c o n j u g a t e b e h a v i o u r o f Pc4 i n t h e m i d - l a t i t u d e s . As f o r t h e h i g h l a t i t u d e s , e a r l i e r o b s e r v a t i o n made by J a c o b s and W r i g h t (1965) have y i e l d e d some r e s u l t s . They s u g g e s t t h a t o s c i l l a t i o n s i n t h e Pc4 r a n g e i n a m p l i t u d e and p e r i o d a p p e a r s i m u l t a n e o u s l y a t t h e c o n j u g a t e s t a t i o n s o f B y r d and G r e a t Whale R i v e r . T h i s a g r e e s w i t h o u r o b s e r v a t i o n s o f more r e c e n t d a t a a l s o f r o m t h e B y r d - G r e a t Whale p a i r . 1 5 9 VI.2 DIURNAL VARIATION OF Pc4 AT THE MID-LATITUDE RALSTON STATION Within the frequency boundary of P c 4 defined by the IAGA r e s o l u t i o n 1 9 6 4 , there are two d i f f e r e n t types of p u l s a t i o n a c t i v i t i e s that may o f t e n be i d e n t i f i e d at Ra l s t o n . Roth types are observed mainly i n the daytime. Ralston under moderately disturbed c o n d i t i o n s (Kp = 3 - 4) i s c a l l e d 'Giant p u l s a t i o n 1 or simply Pg i n t h i s t h e s i s , a f t e r Sucksdorff (1939) who f i r s t discovered t h i s type of phenomenon i n an a u r o r a l region. 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 the frequency i s concerned, Pg i s Pc4, but a Pg i s known to be a very l o c a l phenomenon. The focus of the present research i s mainly on the usual type of Pc4 that occurs under moderately quiet c o n d i t i o n s ( I C .^ l - > 2 ) . This type of Pc4 may be observed simultaneously over a wide area. The d i u r n a l v a r i a t i o n of Pc4 observed at Ralston appears to have a maximum i n frequency around 0600 L.T. and a minimum around noon or e a r l y i n the afternoon. Pc4 occurs at a l e s s frequent rate i n the afternoon than i n the morning, and the afternoon Pc4, when observed, i s u s u a l l y much lower i n s i g n a l strength than that i n the morning. There are occasions, however, when the s i g n a l strength of Pc4 has been found to be greater i n the e a r l y afternoon. Events that The f i r s t type of p u l s a t i o n a c t i v i t y observed at l 6 o occur i n the afternoon with great i n t e n s i t y are observed at R a lston only when the va.lue of the index i s r e l a t i v e l y high. In P i g . VI.2a, an example i s shown where Pc4 had been a c t i v e at Ralston throughout the day, p a r t i c u l a r l y so i n the morning. The maximum-frequency of Pc4 20 mHz) occurred j u s t around 0600 L.T. to reach i t s lowest value of approxi-mately 5 mHz at 1500 L.T. The maximum amplitude of t h i s p a r t i c u l a r Pc4 event i s found to occur around 1000 L.T. which i s the time when the f ^ band of Pc3 becomes s i g n i f i c a n t . The correspondence between the occurrence of Pc4 and the occurrence of the f 0 band of Pc3 at Ralston has been 3 found to be extremely 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 corresponds c l o s e l y to the d i u r n a l p a t t e r n of the f ^ band of Pc3. The maximum frequencies of both the Pc4 and the f ^ bands are found to occur around 0800 L.T. i n the morning whereas the minimum frequencies are observed around l o c a l noon. Both Pc4 and the f_ band of Pc3 were observed to be i n bundles, each bundle re p r e s e n t i n g a packet of waves. Further, the corresponding packets of waves of the two d i f f e r e n t bands appear to be s t r i k i n g l y s i m i l a r . Such correspondence continues, although l e s s e a s i l y recognized, even a f t e r 1400 L.T. when the f ^ band rather than the f ^ band of Pc3 dominates ( i n the sense that i t i s of much greater i n t e n s i t y ) . 1 6 1 T h e r e a r e c a s e s where a r e l a t i v e l y s t r o n g Pc4 s i g n a l i s o b s e r v e d e a r l y i n t h e a f t e r n o o n , b u t t h i s o c c u r s o n l y 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 . The November 13 e v e n t shown i n F i g . V I . 2 c i s one s u c h e x a m p l e where a s t r o n g Pc4 p u l s a t i o n s i g n a l o f 10 mHz I n f r e q u e n c y i s o b s e r v e d a r o u n d 1300 L.T. s o o n a f t e r t h e f ^ b and o f Pc3 becomes n o t i c e a b l e . P r e l i m i n a r y r e s u l t s I n d i c a t e t h a t t h e a m p l i t u d e s o f t h e X and Y c o m p o n e n t s o f Pc4 a r e c o m p a r a b l e i n most c a s e s , b u t 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 d i s t u r b a n c e s i s h i g h , t h e y may d i f f e r , t h e Y component u s u a l l y b e i n g much l a r g e r t h a n t h e X c o m p o n e n t . I n F i g . V I . 2 d , b o t h t h e X and Y c o m p o n e n t s o f t h e F e b r u a r y 9* 1967 e v e n t h a v e b e e n d i s p l a y e d f o r c o m p a r i s o n . T h i s e x a m p l e c l e a r l y d e m o n s t r a t e s t h a t t h e a m p l i t u d e o f t h e Y component o f Pc4 i s much g r e a t e r t h a n i t s X c o m p o n e n t ; i n f a c t , t h e a m p l i t u d e o f t h e X component i s so s m a l l t h a t one f i n d s d i f f i c u l t y i n i d e n t i f y i n g i t , p a r t i c u l a r l y i n t h e a f t e r n o o n . 1 6 2 FIG Vl.2a February 24,1967 DIURNAL VARIATION OF Pc4 163 FIG Vl.2b RALSTON X NOV 9,67 SIMULTANEOUS OCCURRENCE OF Pc3 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 Pc4 The s o - c a l l e d 'Giant P u l s a t i o n ' (Pg) described by various authors and reviewed by Kato (1964) has a l s o been observed at Ralston under moderately d i s t u r b e d conditons. Pg i s known to be a l o c a l phenomenon which occurs at high l a t i t u d e s or i n the a u r o r a l zone. F i g . VI.3a shows a Pg event of approximately 100 sec period observed at M c G i l l and not at the other s t a t i o n s . The Pg a c t i v i t y took place during most of the day of August 17, 1967 but only a small 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 f o r i l l u s t r a t i v e purpose. As f o r the usual type of Pc4 that occurs under moderately quiet magnetic conditons, i t has been widely recognized that t h i s type of Pc4 may be observed simul-taneously over a wide area. Indeed, simultaneous observations made at Great Whale, Ra l s t o n and M c G i l l not only i n d i c a t e t h i s trend, but f u r t h e r , the Pc4 observations are found to be of the same frequency. One t y p i c a l Pc4 event simultaneously observed at Great Whale, 3 y r d , Ralston, 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. The frequency of Pc4 was observed to be the same at a l l s t a t i o n s . The amplitude, however, i s s l i g h t l y greater at Ralston and M c G i l l , but not to a s i g n i f i c a n t extent. The conjugacy of Pc4 f o r both the Byrd-Great Whale 167 p a i r I n the h i g h l a t i t u d e r e g i o n and the E i g h t s - M c G i l l p a i r i n the m i d - l a t i t u d e s has been found to be e x t r e m e l y good. Even peak, t o peak corr e s p o n d e n c e has been obse r v e d between c o r r e s p o n d i n g p a i r o f s t a t i o n s . I t 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 s l o w speed magnetic tape d a t a r e c o r d e d a t Great Whale a r e o f s u f f i c i e n t l y low n o i s e t o s i g n a l r a t i o . T h i s does not a l l o w us t o make a d e t a i l e d comparison o f P c 4 o b s e r v e d at t h e h i g h and the m i d - l a t i t u d e s t a t i o n s . P r e l i m i n a r y 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, have y i e l d e d some i n t e r e s t i n g i n f o r m a t i o n . Sonagrams produced from slow speed tape d a t a r e c o r d e d at Great Whale have shown no d i s t i n c t s e p a r a t i o n between the Pc3 and the Pc4 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 the l o w e r l a t i t u d e s . O f t e n a t R a l s t o n , and l e s s o f t e n , a t C o l l e g e , Pc4 when ob s e r v e d has been found t o be a d i s t i n c t band s e p a r a t e d from the Pc3. No s e p a r a t i o n i s o b s e r v e d when the l e v e l o f magnetic d i s t u r b a n c e i s h i g h , f o r example, i n the event of a magnetic storm. The F e b r u a r y 24, 1967 event shown i n F i g . VI.3c c l e a r l y i l l u s t r a t e s the phenomenon d e s c r i b e d above. One may see on the diagram t h a t no s e p a r a t i o n between the Pc4 and the Pc3 bands has t a k e n p l a c e a t G r e a t Whale c o n t r a r y t o the c l e a r two-band s t r u c t u r e o b s e r v e d at R a l s t o n . The F e b r u a r y 23, 1967 event, which o c c u r r e d 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 , d i d not show c l e a r band s t r u c t u r e a t 168 b o t h Great whale 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 o b s e r v e d at R a l s t o n , and not at Great Whale. FIG Pg ACTIVITY AT McGILL M 170 GW-Y 11.42 r I AT0.5HZ BY-Y BY-X ,2.72r 'AT0.5HZ RA-Y 0.05 r AT0.5HZ MG-Y-, 0.303 r 'AT0.5HZ MG-X ,0.303 r 'AT0.5HZ EI-F , 0.042 r IAT0.5HZ J i i_ 22 SEPT65 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 11 i I 11 i 11 I 11 iI 1 1 1 1 1 11 I I I ' I ' U.T., 0 23,67 24,67 FIG VI.3C LATITUDE DEPENDENCE OF P e s 172 VI.4 DISCUSSION The c o n c e n t r a t i o n of the Pc4 range of p u l s a t i o n near the s u b - a u r o r a l zone observed by v a r i o u s a u t h o r s (Obayashi and J a c o b s , 1958; Veldkamp, i960; Kato and S a i t o , 1962) has suggested t h a t Pc4 may o r i g i n a t e 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 the o b s e r v a t i o n made r e c e n t l y by a r e s e a r c h group r e p o r t i n g from Japan (Hirasawa and Nagata, 1966; Nagata and F u k u n i s h i , 1968) t h a t the d a i l y v a r i a t i o n c u r v e of the 15 mHz band f r e q u e n c y (Pc4) on m o d e r a t e l y d i s t u r b e d days (11 ^ZK^^. 20) i s i n good agreement w i t h a d a i l y v a r i a t i o n c u r v e of the e i g e n f r e q u e n c y of a s t a n d i n g A l f v e n wave a l o n g the f i e l d l i n e s on the plasmapause, t h e o r e t i c a l l y d e r i v e d from C a r p e n t e r ' s model of the plasmapause ( W i l s o n , 1963). A s i m i l a r t r e n d 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 has been observed a t the mid-l a t i t u d e C anadian s t a t i o n s r e p o r t e d i n t h i s c h a p t e r . I n s o f a r as the Pc4 band i s concerned, t h e r e f o r e , the s t a n d i n g A l f v e n wave on the plasmapause may be c o n s i d e r e d as the most p r o b a b l e r e s o n a t o r . . I f t h i s i s i n d e e d the c a s e , s i n c e the e i g e n f r e q u e n c y of a hydromagnetic o s c i l l a t i o n depends h e a v i l y on the d i m e n s i o n of the magnetic r e s o n a t o r , and the d i m e n s i o n s of the plasmapause and of the plasmasphere are c l o s e l y r e l a t e d , i t would not be t o o s u r p r i s i n g t o f i n d the c l o s e correspondence between the o c c u r r e n c e as w e l l as the d i u r n a l b e h a v i o u r of Pc4 and t h a t of the f Q band of Pc3 obser v e d at 1 7 3 R a l s t o n . The s i m i l a r i t y between the K dependence of the f ^ band of Pc3 and that of Pc4 has already been described i n d e t a i l i n the l a s t chapter. One example ( F i g . V I . 3 b ) has been given where the Pc4 a c t i v i t y observed at both mid- and h i g h - l a t i t u d e s t a t i o n s are comparable i n amplitude as w e l l as i n p e r i o d . This type of 'Pc4' could not be i n t e r p r e t e d simply as a r e s u l t of a hydromagnetic o s c i l l a t i o n o r i g i n a t i n g at the plasmapause. Rather, t h i s may be taken as evidence that the eigen frequency of the p o l o i d a l o s c i l l a t i o n described i n the previous chapters may sometimes be found to be very low, so low that i t has passed the lower frequency boundary of P c 3 defined by the Berkeley r e s o l u t i o n . Such an u l t r a -low frequency Pc3 i s observed only under very quiet magnetic c o n d i t i o n s . 174 CHAPTER V I I  POSTCRIPT: DISCUSSION 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 of the ?c3 frequency observed at Ralston i n the year 1967 have been studied i n d e t a i l . I t has been found and reported i n Chapter I I I that the m a j o r i t y of them may be c l a s s i f i e d i n t o f o u r or a combination of four basic types. In order to e x p l a i n the occurrence of d i f f e r e n t basic types of d i u r n a l v a r i a t i o n of Pc3, the existence of an eigen o s c i l l a t i o n of the modified A l f v e n mode In the plasmatrough was proposed i n a d d i t i o n to the eigen o s c i l l a t i o n i n s i d e the plasmasphere already widely b e l i e v e d to e x i s t . Using 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 research i n Chapter IV, the dependence of the four basic types of d i u r n a l v a r i a t i o n on the index has been i n v e s t i g a t e d . The experimental r e s u l t thus obtained f u r t h e r r e i n f o r c e s the idea that eigen o s c i l l a t i o n may indeed e x i s t i n the plasmatrough. In f a c t , the research re-ported i n Chapter IV enables one to i d e n t i f y the frequency component of Pc3 observed at Ralston as having o r i g i n a t e d i n the plasmatrough. A comparative study of simultaneous observations made at both high and m i d - l a t i t u d e s t a t i o n s provides f u r t h e r support f o r the proposed model In that the frequency component be l i e v e d to o r i g i n a t e i n the plasmatrough was found to 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 . T h i s i s c o n t r a r y t o the o b s e r v a t i o n of another component of Pc3 b e l i e v e d t o o r i g i n a t e i n s i d e the plasmasphere, which was o n l y v a g u e l y seen t o e x i s t at the h i g h e r l a t i t u d e s . Thus, a l l e x p e r i m e n t a l r e s u l t s on Pc3 m i c r o p u l s a t i o n r e p o r t e d i n the p r e v i o u s c h a p t e r s has, up t o now, been c o n s i s t e n t .'with the model proposed. I t i s r e g r e t a b l e , however, t h a t no d a t a s i m u l -t a n e o u s l y r e c o r d e d at a l o w e r 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 i n the c o u r s e of t h i s i n v e s t i g a t i o n . F u r t h e r e x p e r i m e n t s must be performed t o determine whether the model proposed i n t h i s t h e s i s i s v a l i d i n the low l a t i t u d e s , or whether i t i s a phenomenon a p p l i c a b l e o n l y i n the h i g h -and m i d - l a t i t u d e s . F u t u r e I n v e s t i g a t i o n should be planned t o l o o k at s i m u l t a n e o u s w h i s t l e r d a t a , as w e l l as any s a t e l l i t e d a t a t h a t may be a v a i l a b l e , so t h a t the e x a c t p o s i t i o n of the plasmapause may be l o c a t e d . So f a r , , w h i s t l e r o b s e r v a t i o n s nave boon the most s u c c e s s f u l i n l o c a t i n g the plasmapause. I f the d i m e n s i o n as w e l l as the c o n f i g u r a t i o n of the plasmapause can be a c c u r a t e l y d e t e r m i n e d , t h e n the d i m e n s i o n o f the plasmasphere and t o a l e s s e x t e n t the p l a s m a t r o u g h may be e s t i m a t e d . F u r t h e r , i f 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 the magnetosphere which a g a i n may be e s t i m a t e d from the w h i s t l e r d a t a i s a l s o known, a s i m p l e o r d e r of magnitude c a l c u l a t i o n based on the 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 i n b o t h hydro-magnetic r e s o n a t o r s 'would 176 enable one to estimate the d i u r n a l v a r i a t i o n of micropulsa-t i o n frequency to be observed at a given s t a t i o n . This, i n t u r n , could be compared w i t h experimental o b s e r v a t i o n . I f the v a l i d i t y of the model may indeed be e s t a b l i s h e d , since a Pc3 i s observed every day, continuous observation over a network of s t a t i o n s s e l e c t e d along a geomagnetic meridian could provide continuous i n f o r m a t i o n on the dimension and the c o n f i g u r a t i o n of the dayside plasmapause, the plasmasphere and the plasmatrough. 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 may be estimated. The existence of eigen o s c i l l a t i o n s i n the magneto-sphere has been assumed throughout t h i s t h e s i s . No s e r i o u s attempt, however, has been made to study the generation' mechanism responsible 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 . Atkinson and Watanabe (1966) have suggested that hydromagnetic i n s t a b i l i t y of the K e l v i n Helmholtz type may generate surface waves i n the magnetopause which may 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 eigen o s c i l l a t i o n s i n the outer magnetosphere, which i n t u r n are responsible 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 . Since the plasmapause i s a boundary between two ' 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 responsible f o r the e x c i t a t i o n of surface waves at the plasmapause, which i n t u r n could produce o s c i l l a t i o n s i n the plasmasphere and the plasmatrough. 177 The sudden enhancement of the two bands of Pc3 a c t i v i t y f o l l o w i n g an i n c r e a s e i n Pc4 i n t e n s i t y , r e p o r t e d i n C h a pter IV, may be t a k e n as e x p e r i m e n t a l o b s e r v a t i o n t h a t s u p p o r t s the t h e o r e t i c a l c o n s i d e r a t i o n g i v e n i n the l a s t p a r a g r a p h . Undoubtedly f u t u r e e x p e r i m e n t s must be p l a n n e d t o l o o k more c l o s e l y I n t o the v a l i d i t y o f such a s u g g e s t i o n . A f u t u r e i n v e s t i g a t i o n s h o u l d a l s o g i v e p r i o r i t y t o a d e t a i l e d s t u d y of Pc4 t o see whether Pc4 may i n d e e d be caused by a hydromagnetic wave propagated a l o n g the f i e l d l i n e at the plasmapause. i n p a r t i c u l a r , the p o l a r i z a t i o n of Pc4 s h o u l d be examined more c l o s e l y . A c l o s e e x a m i n a t i o n of t h e p o l a r i z a t i o n of each of the t h r e e Pc3 bands observed i n m i d - l a t i t u d e s s h o u l d a l s o be v e r y 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 c o n j u g a t e p a i r o f s t a t i o n s can be e s t a b l i s h e d f o r comparison. Only v/ith p r e c i s e knowledge of the p o l a r i z a t i o n of each of the Pc3 and Pc4 bands, can the g e n e r a t i o n mechanism of t h e s e p u l s a t i o n a c t i v i t i e s be u n d e r s t o o d . Such p r e c i s e knowledge would a l l o w one. t o p i n p o i n t the p a r t i c u l a r mode, or c o m b i n a t i o n of d i f f e r e n t modes, of hydromagnetic o s c i l l a t i o n r e s p o n s i b l e f o r t h e i r e x c i t a t i o n . BIBLIOGRAPHY Angerami, J . J . and C a r p e n t e r , D. L. (1966) J . Geophys. Res., Jl, 711 A t k i n s o n , G. and Watanabe, T. (1966) E a r t h and P l a n e t . S c i . L e t t e r , 1, 89 B e r t h o d , W. K., H a r r i s , A. K., and Hope, H. J . (1966) J . Geophys. Res. 6>5_, 613 B o l s h a k o v a , 0. V. and T r o i t s k a y a , V. A. (1964) Symposium on U.L.P. E l e c t r o m a g n e t i c F i e l d s , B o u l d e r , C o l o r a d o . B o l s h a k o v a , 0. V. (1965a) Geomag. and Aeron. j5_, 675 (Eng. Tr a n s . ) B o l s h a k o v a , 0. V. (1965b) A s t r . Zh., 42 (4), 859 B r i c e , N. (1965) J . Atmospheric T e r r e s t . Phys., 2J_, 1 C a h i l l , L. J . J r . and Amazeen, P. G. (1963) J . Geophys. 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(1964) I n N a t u r a l E l e c t r o m a g n e t i c Phenomena below 30 Kc/S (D. P. B l e i l , Ed.) 351, Plenum P r e s s , N.Y. Her r o n , T. J . and H e i r t z l e r , J . R. (1966) N a t u r e , 210, 361 H i r a s a w a , T. and Nagata, T. (1966) Pure A p p l . Geophys., 65, 102 Holmberg, E. R. R. (1951) Ph. D. T h e s i s , U n i v . o f London Holmberg, E. R. R. (1953) M. N. R o y a l A s t r o n o m i c a l Soc., 6 (8), 467 J a c o b s e t a l (1964) J . Geophys. Res., 62 ( l ) , 180 J a c o b s , J . A. and Si n n o , R. (i960) J . Geophys. Res., 65 ( l ) , 107 J a c o b s , J . A. and Watanabe, T. (1964) J . Atmos. T e r r . Phys., 26, 825 J a c o b s , J . A. and Wrigh t , C. S. (1965) Can. J . Phys., 43, 2099 K a t o , Y. and S a i t o , T. (1959) J . Geomag. G e o e l e c , 10, 221 K a t o , Y. and Watanabe, T. (1956a) S c i . Rept. Tohoku U n i v . , S e r . 5, Geophys., 8, 19 K a t o , Y. and Watanabe, T. (1956b) S c i . Rept. Tohoku Univ., S e r . 5, Geophys., 8, 157 K a t o , Y. and 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 on U.L.F. E l e c t r o m a g n e t i c F i e l d , B o u l d e r , C o l o r a d o . Kopytenko Yu. A. and Raspopov, 0. M. (1968) Cosmic R e s e a r c h , 6 ( 4 ) , 617 Kopytenko Yu. A. and Raspopov, 0 . M. (1968) Cosmic R e s e a r c h , 6 ( 4 ) , 6 l l Lawrence e t a l (1965) American GeoDhys. Union M e e t i n g , Washington, D.C. A p r i l , 1965 Lokken, 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 below 30 Kc/S Plenum P r e s s , New York M a i n s t o n e , J . S. (1967) N a t u r e , 21^, 5105 Maole, E. (1959) J. Geophys. Res., 64, 1395 Meldrum, R. D. and Gib 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. and M a i n s t o n e , J . S. (1963) A u s t r a l . J . Phys., 16, 507 Nagata e t a l (1966) P r e s e n t e d a t I n t e r Union Symposium on S o l a r T e r r e s t r i a l P h y s i c s , B e l g r a d e Nagata, T. and F u k u n i s h i , H. (1968^ Geophys. J . R. A s t r . Soc., 1^, 69 N i s h i d a , A. (1966) J.. Geophys. Res., 2 , ( 2 3 ) , 5669 Obayashi, T. (I965) J . Geophys. Res., JO ( 5 ) , I O 6 9 Obayashi, T. and Jacob, J . A. (1958) Geophys. J . R. A s t r . S o c , JL, 53 Pope e t a l (1962) J . Geophys; Res., 62, 3588 S a i t o , T. (1964a) Rep. Ionosph. Space. Res. Japan, 18, 197 S a i t o , T. (1964b) J . Geomag. G e o e l e c t . , 1,6, 115 181 Saito, T. (1966) ESSA, Technical Rep. IER15 - ITSA15 Saito, T. (1967) J. Geophys. Res., J_2 ( 15) , 3895 Siebert, M . (1964) Planet. Space S c i . , 12, 137 Shchepetuon, R. V. (1966) Geomag. I Aeron. Siscoe, G. L. et a l (1969) J. Geophys. Rev., 74 ( 7 h 1759 Snyder, G. W. et a l (1963^ J . Geophys. Res., 1.8, 1361 Stuart, W. F . and Usher, M . J . (1966) Geophys. J. R. Astr. Soc., 12, 71 Troitskaya, V. A. (1967^ Solar - T e r r e s t r i a l Physics, Academic Press Veldkamp, J . ( i 9 6 0 ) J . Atmosph. Terrest. Phys., 17_, 320-324, 1 Voelker, H. (1967) Communication presented i n Symposium Birkeland Watanabe, 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. Technical Memorandum, 66-2 Wentworth, R. C. (1966) J. Geomag. Geoelec., 18 (2), 257 Westphal, K. 0 . and Jacobs, J. A. (1962) Geophys. J. R. Astr. S o c , 6, 360 Wilson, C.R. (1963) Univ. of Alaska 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) Indian J. Meteorology and Geophys., 18, 349 132 SUPPLEMENT TO BIBLIOGRAPHY C a r o v i l l a n o , R. L. and McClay, J. P. \xvop Phys. F l u i d s , 8 , 2006 .Blnsack, J . II. (1967) J . Geophys. Res., 7 2 , 5231 Dungey, J . W. (1964) P e n n s y l v a n i a S t a t e U n i v e r s i t y . I o n o s p h e r i c Research L a b o r a t o r y S c i e n c e Report No. 69 .Kato, Y. and Watanabe, T. (1957) S c i . Rep. Tohoku U n i v . S e r . 5 , Geophys., 8 , 157 R a d o s k i , H. R. and C a r o v i l l a n o , R. L. (1966) Phys. F l u i d s , 9 , 285 R a d o s k i , II. R. (1967) J . Geomag. G e o e l e c , 19 , 1 S a i t o , T. (I960) S c i . Rep. Tohoku U n i v . , Ser 5 , Geophys., 12, 106 Tepley. and Wontv-jorth (1962) J . Geophys. Res., 67 , 3317 T r u s s e l l , D. (1966) U n i v e r s i t y of B r i t i s h Columbia, G e o p h y s i c s B.Sc. T h e s i s 183 APPENDIX 1  CHARACTERISTICS OF THE PLASMAPAUSE U s i n g w h i s t l e r d a t a o b t a i n e d at E i g h t s and B y r d d u r i n g J u l y and p a r t of August 1963, C a r p e n t e r (1966) was a b l e t o deduce the f o l l o w i n g b a s i c f e a t u r e s o f the knee. O b s e r v a t i o n of knee e f f e c t s by s a t e l l i t e has a l s o been made by v a r i o u s o b s e r v e r s ( G r i n g d u z e t a l , i960; T a g l a r e t a l , 1965j Lawrence e t a l , 1965). R e s u l t s o b t a i n e d by s a t e l l i t e o b s e r v a t i o n s were found t o be i n good agreement w i t h r e s u l t s o b t a i n e d u s i n g w h i s t l e r d a t a . a. The knee i s a permanent f e a t u r e o f the magnetosphere. b. F o r c o n d i t i o n s o f 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 the plasmapauge i n the e q u a t o r i a l p l a n e i s d i s p l a y e d i n F i g . 1.2 a f t e r C a r p e n t e r (1966). The p r i n c i p a l f e a t u r e of t h i s c u r v e are as f o l l o w s : ( i ) A r e l a t i v e l y broad minimum i n g e o c e n t r i c d i s t a n c e , c e n t e r e d r o u g h l y on 0600 L.T., the minimum d i s t a n c e i s about 3 - 3.5 R g. ( i i ) A maximum g e o c e n t r i c d i s t a n c e at about, 2000 L.T., the maximum b e i n g about 5 - 5.55 R, ( i i i ) F o l l o w i n g the maximum near 2000 L.T., t h e r e i s a d e c r ease i n the r a d i a l d i s t a n c e o f the plasmapause on the n i g h t s i d e of the e a r t h . The d e c r e a s e I s r o u g h l y 1 .6 R over a p e r i o d of the o r d e r of 10 h o u r s , ( i v ) A r a p i d i n c r e a s e i n r a d i a l d i s t a n c e near 1300 L.T. i n v o l v i n g a v a r i a t i o n of about 1 i n a p e r i o d of about 1 hour. T h i s e f f e c t may o c c u r s e v e r a l h o u r s b e f o r e o r a f t e r l 8 0 0 L.T. w i t h r o u g h l y h a l f of the c a s e s f a l l i n g w i t h i n an hour o r two of 1600 L.T. (v) A g r a d u a l i n c r e a s e i n r a d i a l d i s t a n c e on the day s i d e from about 0600 L.T. t o m i d ^ a f t e r n o o n . The t o t a l range of t h i s v a r i a t i o n i s of the o r d e r of 0.5 R and w i t h i n the p e r i o d t h e r e appears t o be a secondary maximum around 1200 L.T., f o l l o w e d by a secondary minimum around 1400 or 1500 L.T. D u r i n g v e r y q u i e t p l a n e t a r y magnetic c o n d i t i o n s ( i - ^ = 0 1) the above mentioned d i u r n a l c u r v e of the plasmapause moves outward and assumes a more n e a r l y c i r c u l a r c o n f i g u r a t i o n a t i t s l a r g e r r a d i u s . (The h i g h - l a t i t u d e p o s i t i o n of Byrd s t a t i o n becomes f a v o u r a b l e f o r knee o b s e r v a t i o n ( B i n s a c k , 1967) ) . Under stormy c o n d i t i o n s the plasmapause moves inward and the degree of asymmetry w i t h r e s p e c t t o the e a r t h may become more pronounced ( C o r c u f f and D e l a r o c h e , 1'364; C a r p e n t e r , 1 9 6 2 ) . 185 APPENDIX 2 SPECIFICATION OF KAY ELECTRIC SONAGRAPH 7029A FREQUENCY RANGE: DISPLAYS AVAILABLE: ANALYSIS TIME: EFFECTIVE RESOLUTION: AGC RANGE: 5 to 16000 Hz i n s i x ranges; 5 10 20 40 80 160 500 Hz 1000 Hz 2000 Hz 4000 Hz 8000 Hz 16000 Hz Frequency-vs-amplitude-vs-time (conventional) Frequency-vs-amplitude-vs-time (contour) Amplitude-vs-frequency Amplitude-vs-time 1.3 Minutes 5 10 20 40 80 160 500 Hz 1000 Hz 2000 Hz 4000 Hz 8000 Hz 16000 Hz 2.8 and 5.6 and 11.2 and 22.5 and 150 45 and 300 90 and 600 19.0 Hz 37.5 Hz 75 Hz Hz Hz Hz V a r i a b l e 20 to 40 DB down to 10. FREQUENCY CALIBRATION: Switenable at 50, 500, or 1000 Hz i n t e r v a l s . RESPONSE: RECORDING TIME: +2 DB over e n t i r e range. 5 - 500 Hz 38.4 sec 10 - 1000 Hz 19.2 sec 20 - 2000 Hz 9.6 sec 40 - 4000 Hz 4.8 sec 80 - 8000 Hz 2.4 sec 160 - 16000 Hz 1.2 sec AMPLIFIER CHARACTERISTICS: F l a t or 13 DB high-frequency pre-emphasis. INPUT IMPEDANCE: 200, 600, or 10,000 Ohm, switchable 186 APPENDIX 3 POSSIBILITY OF MULTI-BAND Pc3 CAUSED BY HARMONICS Stuart and Usher (1966) found that the Pc spectra at the three B r i t i s h s t a t i o n s show peaks of m i c r o p u l s a t i o n occurrence at 30 sec at Lerwick, 60 sec at Eskdalemuir and 40 sec at Hartland. A secondary peak at 25 sec period i s also observed at Eskdalemuir. 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 of the fundamental period of micrOpulsations 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 then be due to d i f f e r e n t harmonics appearing at each s t a t i o n . In t h i s way a fundamental period might be 120 second of which Lerwick was the f o u r t h harmonic, Hartland the t h i r d , and Eskdalemuir the second and f i f t h . (b) A l a t i t u d e dependence of fundamental period may e x i s t , being 40 sec at Hartland, 60 sec at Eskdalemuir and 90 sec at Lerwick. In t h i s case the observed Lerwick a c t i v i t y may be the t h i r d harmonic, and the secondary peak at Eskdalemuir may be second or t h i r d harmonic. No example, however, has been given i n Stuart and Usher's paper to show the d i u r n a l p atterns observed at d i f f e r e n t s t a t i o n s . To consider whether the multi-band s t r u c t u r e d Pc3 observed at Ralston too may be caused by higher harmonics of a p a r t i c u l a r fundamental frequency, as suggested by Stuart and Usher (1966) mentioned above or by Mainstone (1966), we have considered the f o l l o w i n g : Let be the fundamental frequency of a given s t a t i o n a t a given time t . th t h Suppose that only the n and the n+m harmonics are observed at that s t a t i o n at time t of a given day, that i s • = n F, n, t t ' n+rn, t (n+m) F, Then the separation between the two harmonics observed at time t i s n+m, n = f n+m, t f n , t = raFt At a l a t e r time T, i f the fundamental frequency of the given s t a t i o n changes to F^.+T, since only a continuous event i s to be considered, the harmonics observed would be fn,t+T = n Ft+T f = (n+m)-F n+m, t+T v ' t+T ,nd ,t+T n+m, n m F t+T and the r a t i o „t+T F n+m,t+T 'n+m, t n, t 188 which i m p l i e s that as the fundamental frequency i n c r e a s e s (or decreases), the separation between two harmonic bands should a l s o increase (or decrease). I f the multi-band s t r u c t u r e d Pc3 observed at Ralston i s caused by harmonics, i t should behave as p r e d i c t e d above. However, observations of February 11 (Feb. I I I . 2 b ) , September 3, and October, 1967* f o r example, Ind i c a t e that t h i s i s not the case. Thus the e f f e c t of higher harmonics alone cannot be responsible f o r the existence of the m u l t i -band Pc3 observed. 189 APPENDIX 4 TABLE OF THE K INDEX FOR DATES ILLUSTRATED IN FIGURES 1 2 3 4 5 6 7 8 ^ P Jan 21, 1964 X 0 0 0 + 0 0 0 0 0 0 °+ °+ 3 + Apr 18, 1964 X 1_ 2o 4 0 X 5_ 4_ X 24_ June 15, 1965 1 + 2_ 1 + \ 4 0 A 5_ 4 + June 24, 1965 1_ . °+ 0 + i _ X 1 0 °+ X Sept 16, 1965 X 4_ X 4 + X 3, T \ 35_ Sept 18, 1965 X X X 1 + X 4_ 4 + 2 3 + Sept 19, 1965 2, T 3_ • 4 0 3_ X 4_ 4_ 2o- 2 5 0 Sept 20, 1965 1 O l _ 2o 2_ X X 2o Dec 14, 1965 Oo l o 0 o 0+ 1- 1- 0+ 1+ 4+ Dec 17, 1965 °e °o °o 1_ 0, ! 0 °o 1_ 3_ Dec 19, 1965 X 1_ 2_ °+ °o 1_ 2_ 2_ n o Aug 22, 1966 1_ 1_ 1 0 0 0 1_ 3_ 2_ 2o Dec 26, 1966 4_ 3_ X 4 0 4_ 5_ 4_ 4 + 3°o Feb 9, 1967 X X 3, T 1_ 1_ °+ X 1_ 1 3 _ Feb 10, 1967 0 0 1 + °+ 1_ 1_ 0 0 0 0 0 0 3 0 Feb 11, 1967 X 4_ 4_ X X 2_ 19_ Feb 12, 1967 X °o °+ 1_ 1_ i _ o + 1 4-Feb 17, 1967 X 4. 0 \ 3 0 3 o 3 G 2o 3 . 2 3 + Feb 23, 1967 X X 2_ 3 + 4 0 22_ Feb 24, 1967 X' 0 0 2o 1 + 1_ 1 0 X X 19D Date 1 2 3 KP 4 5 6 7 8 £K P Feb 26, 1967 3 0 2o 2 + 2o 2o 2o 20_ Mar is! 1967 1_ 4_ 3_ 3, T 3 0 6+ 3 0 2o 25_ Mar 26, 1967 1 + 0 0 0 2_ 2_ 1 0 2_ 9_ Mar 27, 1967 4_ \ 3 0 4_ 3 + 3_ 3 0 2 6 o May 10, 1967 \ 2_ 1 + 3_ 2o 2o 2o May 22, 1967 \ X o ' l , T 1_ o + 0 + 0 •f 0 0 6 + Aug 9, 1967 \ 1_ 1 0 V 3_ 3 Q \ 2_ 13_ Aug 23, 1967 \ 2_ V l _ 1 0 3_ 1 Aug 24, 1967 •3_ X o 2_ 2 + 2o 2o 2_ 2o 15, Aug 25, 1967 2o 3_ 3o 3 0 2 + 3 0 •5 -'o 4 0 2 3 0 Sept 1, 1967 3 + 34- 5_ 2 + 4 3 G 4 0 5_ 29 _ Sept 7, 1967 \ 1 O 2_ l _ \ 4 + 2_ 1 0 14 0 Oct 4, 1967 2_ 1, -r 1_ °+ ° + °+ 1_ 3_ 8 0 Oct 5, 1967 2_ 2o 2_ 2_ 2 + 2o l 0 15_ Oct 12, 1967 4 + 4 0 4_ 3 0 1_ 4_ 4 0 24+ Oct 16, 1967 2o 2o \ l 0 o + 1_ 2_ 2_ Oct 13, 1967 2_ 2o 2^ 2 + 1_ 1_ 3_ 14_ Oct 25, 1967 1_ ° + 1_ 1 0 0 + 1_ 1 0 l _ Oct 2b, 1967 °+ \ °+ l _ 1_ °+ 1_ . i _ 5_ Oct 29, 1967 3 0 3_ 4 0 5 0 3, T 2^ 29 _ Oct 30, 1967 \ 5+ 4_ 2_ 1 0 1 + 1, T 1 0 19_ Nov 9, 1967 3_ 2o 2o 2o 3 0 3o 3 0 1_ 18 + Nov 13, 1967 3 G ^0 3_ 3o 2, T 3o 4_ 4_ Nov 15, 1967 0 + 1 0 2_ 1 0 4_ 3+ 3 + 191 D a t e V p S K_ • 1 2 3 4 5 6 7 8 - p Nov 17, 1967 1_ 1 0 + 0 0 0 + 0 0 0 + 0 + 3_ Nov . l o , 1967 1 0 ]_ 1_ 1_ n + 1 0, 0 ^ _ Nov 19, 1967 1_ 2_ 1_ 1+ 1 0 0 . 0 6 + Dec 1967 2_L 4 2_,_ 4_ 4 0 4-0 3 + 4^ 2u_ Dec 7, 1967 4, + ). 0, -r 4_ 4 0 9 . 0 27, "r Dec 28, 1967 T o 1_ 0 + 1_ 1 2^ 9. 

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