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An analysis of short period (10-30 seconds) geomagnetic micropulsations Hassett, John Henry 1960

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AN'-ANALYSIS OF SHORT PERIOD (10 - 30 SECONDS) GEOMAGNETIC MICROPULSATIONS by JOHN HENRY HASSETT B.A., U n i v e r s i t y o f B r i t i s h Columbia, 1950 A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE In the Department of PHYSICS We accept t h i s t h e s i s as conforming  to the r e a u i r e d  THE UNIVERSITY OF BRITISH COLUMBIA APRIL, I960  standard  In presenting the  this  r e q u i r e m e n t s f o r an  thesis in partial advanced degree a t  of B r i t i s h Columbia, I agree that it  freely  a v a i l a b l e f o r r e f e r e n c e and  agree that for  the  permission f o r extensive  s c h o l a r l y p u r p o s e s may  D e p a r t m e n t o r by  be  gain  s h a l l not  Department o f  be  a l l o w e d w i t h o u t my  FHVSIC5  The U n i v e r s i t y o f B r i t i s h V a n c o u v e r #, C a n a d a . Date  13  APR  (>D  shall  study.  I  Columbia,  the  of  University  copying of  his representatives.  copying or p u b l i c a t i o n of t h i s  the  Library  g r a n t e d by  that  fulfilment  make  further this  Head o f  thesis my  I t i s understood  thesis for written  financial  permission.  -  i  -  ABSTRACT Geomagnetic m i c r o p u l s a t i o n s are d e s c r i b e d possible origins discussed.  and  Previous work i n Canada  i s reviewed w i t h p a r t i c u l a r a t t e n t i o n to the normal daytime Pc o s c i l l a t i o n s with periods from 10 - 30 seconds.  A d e s c r i p t i o n i s given of the work done  c o r r e l a t i n g the amplitude e x c i t i n g v e c t o r at two Field August 1959  and  d i r e c t i o n of the  stations.  work at R a l s t o n , A l b e r t a during J u l y i s described  in detail.  A digital  computer  i s used to o b t a i n the a u t o - c o r r e l a t i o n c o e f f i c i e n t  and  the covariance of the h o r i z o n t a l components of the vector.  From these two  frequency, are  amplitude,  paramenters the dominant  and  p o l o r i z a t i o n of the v e c t o r  obtained. The  c o n c l u s i o n i s reached  seem to occur frequency.  that normal daytime  i n a small band centred  Two  around a dominant  such dominant f r e q u e n c i e s may  occur  simultaneously  and  the v e c t o r s can have d i f f e r e n t  polarization.  The  amplitude  and  Pc's  d i r e c t i o n of a given  Pc seems to f o l l o w a closed d i u r n a l p a t t e r n reaching a maximum s l i g h t l y before l o c a l noon.  - i i-  TABLE OF CONTENTS Abstract  i  Table o f Contents  i i  Acknowledgements  i i i  Chapter I  II  III  IV  V  VI  1  Introduction (a)  Morphology o f Geomagnetic M i c r o p u l s a t i o n s  (b)  Origin of Micropulsations  ..  P r e v i o u s I n v e s t i g a t i o n s i n Canada (a)  Defence R e s e a r c h Board  (b)  Subsequent  (c)  U n i v e r s i t y o f B r i t i s h Columbia  I n v e s t i g a t i o n s by P.N.L  F i e l d Work, R a l s t o n A l b e r t a , I J u l y - 15 August 1959  1 3 6 6 12 13 14  (a)  Equipment  14  (b)  S t a t i o n Locations  16  (c)  F i e l d Work H i s t o r y  17  E v a l u a t i o n o f Data  20  (a)  C h o i c e o f Records F o r A n a l y s i s  20  (b)  S t a t i s t i c a l A n a l y s i s o f Data  21  Results  24  (a)  Dominant  Frequencies  (b)  D i r e c t i o n and A m p l i t u d e o f the H o r i z o n t a l Vector  24 25  Conclusions  27  Bibliography  29  DIAGRAMS Figure  Facing  Page  2  (1)  Examples of M i c r o p u l s a t i o n s  .  (2)  (a)  Block Diagram S t a t i o n o<  15  (b)  Block Diagram S t a t i o n p  15  (3)  Auto-Correlation Function  31  24  (4)  Auto-Correlation Function  9  24  (5)  Auto-Correlation Function  Showing  Two  (6)  24  25  (7)  R e l a t i v e Amplitudes 31 J u l y , 7 August,  (8)  Polqr P l o t 31 J u l y , 7 August,, 10 August .  26 26  ACKNOWLEDGMENTS  The  author wishes to thank the s t a f f o f  the P a c i f i c Naval Laboratory take part i n the f i e l d  for permitting  him to  work and f o r t h e i r prompt  t r a n s m i s s i o n o f the recorded  data whenever p o s s i b l e .  Thanks are extended to the' s t a f f o f the U n i v e r s i t y o f B r i t i s h Columbia Computing Center and i n p a r t i c u l a r to Mr. R. D e b e l l f o r h i s a s s i s t a n c e i n programming the d a t a . Dr. J.A. Jacobs i s thanked f o r suggesting the investigation,  and f o r h i s c o n s t r u c t i v e help i n  e v a l u a t i n g the d a t a . F i n a n c i a l support  from the N a t i o n a l Research  C o u n c i l o f Canada i s a l s o g r a t e f u l l y acknowledged.  CHAPTER I INTRODUCTION -Morphology o f Geomagnetic M i c r d p u l s a t i o n s .. G e o m a g n e t i c m i c r o p u l s a t i o n s a r e s m a l l s c a l e p e r i o d i c changes i n t h e e a r t h ' s magnetic f i e l d . these  f l u c t u a t i o n s h a v e an o r d e r  The a m p l i t u d e s  of  o f magnitude o f C l ^ t o ,  on o c c a s i o n , a s much a s 20 o r 3 0 ^ ( 1 ^  -  1 gamma  oersted).  They o c c u r  throughout a frequency  from about  .001 c p s up t o a b o u t s e v e r a l c p s .  - 10 *~  range o f Such  m i c r o p u l s a t i o n s h a v e b e e n known s i n c e l 8 6 l and some o b s e r v a t i o n a l s t u d i e s w e r e made d u r i n g t h e f i r s t of t h i s century,  although  work has been c a r r i e d  most e x p e r i m e n t a l  out during  the past  half  and t h e o r e t i c a l  ten years.  M i c r o p u l s a t i o n s have b e e n b r o a d l y c l a s s i f i e d three  groups but recent  (Jacobs  data obtained  I960) i n d i c a t e t h a t these  into  d u r i n g t h e I.GkY.  c l a s s i f i c a t i o n s are too  g e n e r a l and f u r t h e r s u b - c l a s s i f i c a t i o n s p o s s i b l y u s i n g different  c r i t e r i a than  i n t h e p a s t , may be  necessary.  These t h r e e types o f m i c r o p u l s a t i o n s a r e Pc's ( p u l s a t i o n s c o n t i n u e ! ) , P t ' s ( t r a i n s de p u l s a t i o n s ) , and P g s ( g i a n t 1  pulsations).  I n a d d i t i o n t o any observed  signal  there  i s a l w a y s a g e n e r a l b a c k g r o u n d made u p , p a r t l y o f i n s t r u m e n t a l n o i s e , p a r t l y o f induced  power  frequency  s u b - h a r m o n i c s , and p a r t l y o f v e r y l o w a m p l i t u d e P c ' s . When d i s c u s s i n g a p a r t i c u l a r the higher  frequency  end o f t h e f r e q u e n c y  especially  towards  spectrum i t i s w e l l t o  remember t h a t a s i g n a l i s n o t u s u a l l y made up o f t h e one  FIG. I  TYPICAL SIGNAL BASE STATION RALSTON, ALTA II AUG, 59  0024Z  oo 332  Xcc  Yet  X  SHOWING LONGER  0I56Z  MODULATION PERIOD  FROM  SIGNAL 02 07Z  II AUG, 59  MATV  4  INITIATION  OF  PC  AFTER  QUIET  PERIOD  05  X^  Pt  SHOWING  DAMPING  HZ  - 2 -  d i s c r e t e frequency t h i s dominant  but o f a s m a l l band c e n t r e d  around  frequency,  Pc's as t h e i r name suggests t r a i n s w i t h amplitudes  are continuous  wave  a few t e n t h s o f a / and p e r i o d s  from about t e n seconds t o under a minute.  They occur  most f r e q u e n t l y d u r i n g d a y l i g h t hours p a r t i c u l a r l y d u r i n g the l a t e morning and a s e r i e s o f P c ' s may cover a time period l a s t i n g s e v e r a l hours.  (See f i g u r e  1)  P t ' s u s u a l l y occur as a s e r i e s o f o s c i l l a t i o n s and appear t o be w e l l damped w i t h l a r g e r a m p l i t u d e s and l o n g e r p e r i o d s than P c ' s .  They appear i n groups a t  n i g h t w i t h a t o t a l d u r a t i o n o f from t e n minutes t o l e s s than an hour. and  Amplitudes  a r e around one h a l f gamma  p e r i o d s o f t h e o r d e r f o r t y seconds t o s e v e r a l m i n u t e s .  (See f i g u r e Pg's  1).  are s e r i e s of regular p u l s a t i o n s with large  amplitudes  up t o tens o f gammas and p e r i o d s o f a few  minutes o c c u r r i n g o n l y i n t h e a u r o r a l zones. The  p u l s a t i o n s d e s c r i b e d cover t h e f r e q u e n c y  spectrum up t o 0 . 1 cps.  From 0 . 1 t o 10 cps t h e observed  p u l s a t i o n s a r e i n g e n e r a l v e r y weak a l t h o u g h t h e r e a r e c h a r a c t e r i s t i c t r a i n s o f o s c i l l a t i o n s , which have been c a l l e d " P e a r l s " by T r o i t s k a y a ( 1 9 5 7 ) .  Still  higher  f r e q u e n c i e s a r e caused f o r t h e most p a r t by l i g h t n i n g discharges  (Goldberg  1956) o r a r i s e from man-made  background o f e l e c t r o m a g n e t i c  radiation.  D e s p i t e t h e l a r g e amount o f r e c e n t work on  - 3 -  m i c r o p u l s a t i o n s i t i s d i f f i c u l t t o draw more than v e r y g e n e r a l c o n c l u s i o n s about such p r o p e r t i e s as f r e q u e n c y of occurrence,  d i u r n a l and s e a s o n a l v a r i a t i o n ,  latitude  dependance, and whether t h e i n c i d e n c e o f a g i v e n p u l s a t i o n I s l o c a l or widespread.  Often the experimental  d a t a r e p o r t e d by d i f f e r e n t o b s e r v e r s  i s contradictory  or seems t o f i t no r e g u l a r p a t t e r n .  Among t h e p o s s i b l e  r e a s o n s f o r t h i s i s the use o f i n s t r u m e n t s  with different  s e n s i t i v i t i e s , and r e c o r d i n g f o r p e r i o d s o f t o o s h o r t a duration. Another d i f f i c u l t y i s t h e c h o i c e o f method f o r a n a l y s i s o f d a t a and c h o i c e o f c r i t e r i a f o r d i f f e r e n t i a t i n g between t h e d i f f e r e n t t y p e s o f m i c r o p u l s a t i o n s . respect  In t h i s  i t now appears l i k e l y t h a t Pg's can be d i v i d e d  i n t o two groups depending on t h e wave form and time o f maximum f r e q u e n c y  of occurrence.  i n v e s t i g a t o r s (Jacobs Pc's 5-15  A l s o a group o f R u s s i a n  i 9 6 0 ) suggest t h e d i v i s i o n o f  i n t o t h r e e groups w i t h p e r i o d s i n t h e range from seconds, 20 - 40 seconds, and 50 - 90 seconds.  Origin of Micropulsations There i s l i t t l e doubt t h a t t h e source o f t h e d i s t u r b a n c e which causes m i c r o p u l s a t i o n s i s e i t h e r i n the e a r t h ' s i o n o s p h e r e ,  i n t h e o u t e r atmosphere  extending  out t o s e v e r a l e a r t h r a d i i , o r i n both depending on t h e type o f p u l s a t i o n .  I t i s a l s o g e n e r a l l y accepted  that  these v a r i a t i o n s a r e due t o a f l u x o f s o l a r p a r t i c l e s ,  probably  i o n i z e d hydrogen, which a r e i n c i d e n t upon  the e a r t h ' s atmosphere e i t h e r i n t h e form o f an i o n i z e d cloud o r as a s t e a d y  j e t whose i n t e n s i t y and v e l o c i t y  depend on t h e s t a t e o f t h e sun's c o r o n a .  A n a r t from  these r a t h e r general ideas, there are s e v e r a l c o n f l i c t i n g t h e o r i e s d e a l i n g w i t h t h e exact  cause o f the m i c r o p u l s a t i o n s  themselves. Bennett and H u l b u r t  (1954) have suggested t h a t t h e s e  streams o f p r o t o n s from the sun undergo magnetic f o c u s i n g and s p i r a l i n towards t h e e a r t h along l i n e s of force causing w i t h the h e a v i e r  self-  the magnetic  t h e a u r o r a when stopped by c o l l i s i o n s  gas m o l e c u l e s .  M i c r o p u l s a t i o n s might be  caused by i o n i z e d p a r t i c l e s f o l l o w i n g o r b i t s i n t h e e a r t h s magnetic  field.  I f an i o n i z e d c l o u d o f s o l a r o r i g i n e n t e r s t h e e a r t h s upper atmosphere then i t i s p o s s i b l e t h a t hydromagnetic o s c i l l a t i o n s would be e x c i t e d and A l f v e n waves propogated along t h e magnetic l i n e s o f f o r c e  causing  micropulsations  w i t h p e r i o d s comparable to those o f Pt - type o s c i l l a t i o n s . C a l c u l a t i o n s based on observed d a t a and assuming t h a t the m i c r o p u l s a t i o n s a r e caused by A l f v e n waves ( O b a y a s k i and Jacobs 1958)  gives i o n d e n s i t i e s f o r the outer  comparable w i t h f i g u r e s o b t a i n e d  from o t h e r  atmosphere  sources.  Giant p u l s a t i o n s may be caused by t o r s i o n a l o s c i l l a t i o n s i n t h e o u t e r atmosphere (Kato and Akasofu 1956? Kato and Watanabe 1957)  and Pc's by r > o l o i d a l o s c i l l a t i o n s .  would then be i n i t i a t e d  i n t h e s u n l i t p a r t o f the  Pc's  - 5 ionosphere There Shand  1958)  by t u r b u l e n t i s however which  continent-wide  shock  some  shows  waves  experimental  that  i n occurrence,  t h e sun's data  corona.  (Duffus  and  P c ' s and P t ' s a r e o f t e n n o t and  are  o f t e n out o f phase.  This  the  poloidal oscillation  theory  investigators.  from  even  would  when  n o t seem  widespread to  o f the Japanese  favour  CHAPTER I I PREVIOUS INVESTIGATIONS Defence R e s e a r c h  IN CANADA  Board  A group from t h e P a c i f i c N a v a l L a b o r a t o r y (P.N.L.) at E s q u i m a l t B.C. have been r e c o r d i n g Pc's and P t s s i n c e 1  1954.  Most o f t h e i r e x p e r i m e n t a l work has been c a r r i e d  on a t A l b e r t Head, a s t a t i o n on t h e c o a s t near  Victoria,  a l t h o u g h d a t a has a l s o been r e c o r d e d by a mobile at v a r i o u s i n l a n d l o c a t i o n s .  station  Whenever t h e mobile  station  was o p e r a t e d , t h e base s t a t i o n a t A l b e r t Head r e c o r d e d as w e l l f o r comparison.  Measurements were made o f t h e  t h r e e components X, Y, and Z where X ( g e o g r a p h i c a l n o r t h ) , and Y ( e a s t ) a r e t h e components o f t h e h o r i z o n t a l f i e l d H and Z i s t h e v e r t i c a l component  ( p o s i t i v e downwards).  D u f f u s and Shand (1958) o b t a i n e d m i c r o p u l s a t i o n r e c o r d s a t A l b e r t Head i n t h e f r e q u e n c y range cps on 150 days between 1954 and 1957.  .001 t o .1  The magnitude and  d i r e c t i o n o f t h e m i c r o p u l s a t i o n s were noted and i n t e r p r e t a t i o n s made o f t h e d i u r n a l v a r i a t i o n , t h e d i r e c t i o n o f t h e e x c i t i n g v e e t o r j and i t s g e o g r a p h i c a l d i s t r i b u t i o n . The r e s u l t s were compared w i t h d a t a p u b l i s h e d by o t h e r i n v e s t i g a t o r s i n d i f f e r e n t p a r t s of the world et a l 1954,Haimberg  (Chernosky  1953, T r o i t s k a y a 1955).  D u f f u s and Shand found a t r e n d f o r i n c r e a s i n g a m p l i t u d e w i t h i n c r e a s i n g p e r i o d and found t h a t t h e p r o b a b i l i t y o f o c c u r r e n c e depended both on f r e q u e n c y (and hence a l s o on a m p l i t u d e ) and on L.M.T.  The d i u r n a l  v a r i a t i o n s showed o n l y g e n e r a l trends and o f t e n the results conflicted  with those from other  T h i s i s p a r t l y due  to i n s u f f i c i e n t data but a l s o , to a  l a r g e extent, to d i f f e r e n t d e t e c t i o n and equipment.  investigators.  amplification  O f t e n equipment w i l l tend to d i s c r i m i n a t e  a g a i n s t c e r t a i n f r e q u e n c i e s i n favour of o t h e r s or have d i r e c t i o n a l char-act e r i s t i c s thus g i v i n g  incomplete  results.  There Is a l s o the problem of I n t e r p r e t i n g data obtained i n different  geographical locations p a r t i c u l a r l y  latitudes.  Despite these d i f f i c u l t i e s a g e n e r a l peak i n  the Pc a c t i v i t y was  found  s l i g h t l y before l o c a l noon and  a peak i n Pt a c t i v i t y before l o c a l midnight. quietest  time was  from  1800  The  to 2200 L.M.T.  Most of the p u l s a t i o n s had two  in different  phase d i f f e r e n c e s between  or a l l three of the components.  The  g e n e r a l trend  f o r X and Z to be i n phase while Y led or lagged. was  was  This  not i n accord with e a r l i e r work i n Janan (Terada  1917)  where the h o r i z o n t a l components were i n phase and Z lagged. The data f o r s i g n a l s which were i n phase gave a r a t h e r wide s c a t t e r f o r the d i r e c t i o n of the v e c t o r as a f u n c t i o n of frequency.  There was  azimuth  the i n c l i n a t i o n f o r the very low  and  end o f the spectrum. the azimuth  It was  the g r e a t e r was  I n c l i n a t i o n s ranged to 20°  s l i g h t l y less scatter  from  10°  i n both the frequency  n o t i c e a b l e that the g r e a t e r the angle of to  70° and  inclination. azimuths from 260°  true.  Little  c o r r e l a t i o n was  found  between the  vertical  - 8 components a t A l b e r t Head and H a l i f a x Nova S c o t i a where some d a t a had been recorded The  w i t h i d e n t i c a l equipment.  s i g n a l s were u s u a l l y d i f f e r e n t i n f r e q u e n c y  and phase.  When s i m i l a r p u l s a t i o n s d i d o c c u r they seemed t o be e i t h e r e x a c t l y i n phase o r 180°out o f phase w i t h some of a d i u r n a l v a r i a t i o n .  evidence  T h i s c o n f l i c t s w i t h some  observations i n d i c a t i n g that i n i t i a t i o n  i s world-wide  ( T r o i t s k a y a 1955). Because o f t h e o f t e n c o n t r a d i c t o r y d a t a from r e c o r d s at  w i d e l y separated  sequently decided  s t a t i o n s t h e group a t P.N.L. sub-  t o i n v e s t i g a t e s h o r t range g e o g r a p h i c a l  variations i n micropulsations.  Simultaneous  r e c o r d s were  made a t two s t a t i o n s , t h e base s t a t i o n a t A l b e r t Head and the m o b i l e  field  s t a t i o n which occupied  various locations  between May 1958 and F e b r u a r y 1959. Observations  were i n i t i a l l y r e s t r i c t e d  to the  f r e q u e n c y band between 0.001 and 0.1 cps w h i c h was l a t e r extended t o i n c l u d e f r e q u e n c i e s up t o 1 cps.  Measurements  were made o f t h e t h r e e components X, Y, and Z, and a n a l y s i s was by v i s u a l i n s p e c t i o n o f t h e a m p l i t u d e s and p e r i o d s on s t r i p - c h a r t r e c o r d i n g s . to  d e t e r m i n e phase r e l a t i o n s h i p s .  No attempt was made There was a s e l e c t i v e  c h o i c e o f d a t a f o r a n a l y s i s and s i g n a l s w i t h phase d i f f e r e n c e s between components o f IT/A o r more were not processed. The  first field  s t a t i o n was a t Bear Creek some 25  m i l e s from A l b e r t Head and t w e l v e m i l e s from t h e s e a .  - 9 D u f f u s et a l (1959) found t h a t f o r p e r i o d s under two minutes t h e X component a t Bear Creek was as much as 50 per cent l a r g e r than X a t A l b e r t Head w h i l e the Y and i n p a r t i c u l a r the Z component at Bear Creek became smaller w i t h increasing frequency.  I f the amplitudes  o f the t h r e e components a r e summed v e c t o r i a l l y the " t o t a l pulsating vector" i s obtained.  The a m p l i t u d e o f t h e t o t a l  p u l s a t i n g v e c t o r at Bear Creek was l e s s than t h a t at A l b e r t Head f o r p e r i o d s under 50 seconds but g r e a t e r f o r p e r i o d s over 100  seconds.  Thus t h e v e c t o r at t h e s t a t i o n by the sea had a much g r e a t e r i n c l i n a t i o n and i t s a z i m u t h was more w e s t e r l y than t h a t at the i n l a n d s t a t i o n .  Also w i t h increasing frequency  the a m p l i t u d e by t h e sea became g r e a t e r t h a n t h e a m p l i t u d e inland.  I t seems p r o b a b l e t h a t these e f f e c t s a r e due t o  the h i g h e r e l e c t r i c a l c o n d u c t i v i t y o f t h e s e a . The second f i e l d  s t a t i o n was s e t up a t Summerland  B.C.  250 m i l e s from A l b e r t Head and 185 m i l e s from the s e a . Records from Summerland d i f f e r e d from those a t A l b e r t Head much more than those a t Bear Creek  (Shand  et a l 1959).  There were s t i l l however many s i m i l a r i t i e s and c o r r e s p o n d i n g s e c t i o n s o f t h e r e c o r d s c o u l d be compared. The X and Y components at Summerland were s i m i l a r t o those at A l b e r t Head except t h a t a m p l i t u d e s at Summerland averaged  50 per cent h i g h e r .  The Z component at Summerland  was v e r y d i f f e r e n t i n appearance amplitude.  and had a much s m a l l e r  At Summerland t h e i n c l i n a t i o n was much l e s s  - 10 and  t h e azimuth s l i g h t l y more n o r t h e r l y than a t A l b e r t  Head.  The amplitude  f o r t h e t o t a l v e c t o r was about the  same at each s t a t i o n . A third field  s t a t i o n was e s t a b l i s h e d at R a l s t o n ,  A l b e r t a 515 m i l e s from A l b e r t Head and 470 m i l e s from the s e a . The number o f r e c o r d s e c t i o n s which could be compared was r e l a t i v e l y few a l t h o u g h  the onset and  d i s a p p e a r a n c e o f b u r s t s o f a c t i v i t y appeared and  simultaneously  t h e envelopes o f a s e r i e s o f p u l s a t i o n s were s i m i l a r  at t h e two s t a t i o n s . The X components were s i m i l a r i n appearance w i t h the a m p l i t u d e  at R a l s t o n u s u a l l y about double t h a t at  A b l e r t Head.  The Y components were o n l y seldom s i m i l a r  although  a g a i n t h e s i g n a l a t R a l s t o n was u s u a l l y double  t h a t at A l b e r t Head. w i t h a much lower  The Zcomponents were d i s s i m i l a r  amplitude  the h i g h e r f r e q u e n c i e s .  a t R a l s t o n , p a r t i c u l a r i l y at  The azimuth was a l i t t l e more  n o r t h e r l y at R a l s t o n than at A l b e r t Head and the i n c l i n a t i o n much l e s s -- even l e s s than t h a t at Summer l a n d . amplitude  The mean  o f t h e t o t a l v e c t o r a t R a l s t o n was 50 per cent  g r e a t e r than at A l b e r t Head. When t r a i n s o f Pc a c t i v i t y were compared between R a l s t o n and A l b e r t Head t h e y almost always o c c u r r e d s i m u l t a n e o u s l y d e s p i t e a d i f f e r e n c e i n l o n g i t u d e o f 13° . There was a l s o no i n d i c a t i o n o f any d i u r n a l v a r i a t i o n i n t h e amplitude  o f t h e t o t a l v e c t o r at R a l s t o n as  compared t o A l b e r t Head.  - 11 The f o u r t h and l a s t f i e l d  s t a t i o n i n t h i s s e r i e s was  e s t a b l i s h e d at Borrego S p r i n g s , C a l i f o r n i a , 960 m i l e s from A l b e r t Head and o n l y 70 m i l e s from t h e sea.  The  s i g n a l a t B o r r e g o , t h e lower l a t i t u d e s t a t i o n , was s i m p l e r i n form t o t h a t at A l b e r t Head and t h e X and Y components showed fewer phase d i f f e r e n c e s . the  I n d i v i d u a l p u l s a t i o n s at  two s t a t i o n s were seldom s i m i l a r but a g a i n the  envelopes o f s e r i e s o f p u l s a t i o n s were v e r y s i m i l a r . The a m p l i t u d e s o f the X and Y components at Borrego averaged 3/4 t h o s e at A l b e r t Head.  The Z component at  Borrego was much s m a l l e r t h a n t h a t at A l b e r t Head. were l a r g e and f r e q u e n t changes the  There  i n azimuth a t Borrego -  p r e f e r r e d d i r e c t i o n o f t h e t o t a l v e c t o r was n o r t h e a s t  with a slight  inclination.  Summarizing  t h e d a t a from t h e f o u r f i e l d  stations  and the base s t a t i o n at A l b e r t Head, i t seems f e a s i b l e to d i v i d e t h e s i g n a l i n t o t h r e e bands w i t h p e r i o d s i n the  ranges I  -  8,  10 - 30, and above 40 seconds.  The  lower l i m i t o f 1 second i s an i n s t r u m e n t a l l i m i t a t i o n . The group above 40 seconds would i n c l u d e P t ' s .  The group  from 10 - 30 seconds o c c u r r e d most r e g u l a r i l y and i n c l u d e d Pc's r e c o g n i z e d as the normal daytime s i g n a l .  Almost  w i t h o u t e x c e p t i o n t h i s group o c c u r r e d s i m u l t a n e o u s l y at both the f i e l d  s t a t i o n and at A l b e r t Head.  The t o t a l  v e c t o r f o r t h i s m i d d l e group o f Pc's m a i n t a i n e d a p r e f e r e n c e f o r d i r e c t i o n , time o f day, and a m p l i t u d e at the  field  s t a t i o n d i f f e r e n t t o t h a t at A l b e r t Head.  -  12  -  T o t a l Pc a c t i v i t y does n o t appear t o be r e l a t e d s o l e l y t o L.M.T., d e s p i t e t h e p r e f e r e n c e the 10 - 30 second group.  f o r daytime o f  The s t a t i o n at R a l s t o n which  was c l o s e s t t o t h e a u r o r a l zone and f u r t h e s t i n l a n d , and s i t u a t e d i n t h e most u n i f o r m  topography had t h e s m a l l e s t  Z component and t h e l a r g e s t amplitude The  o f the t o t a l vector.  s t a t i o n a t Borrego f u r t h e s t from t h e a u r o r a l zone had  the s m a l l e s t a m p l i t u d e  f o r t h e t o t a l v e c t o r and was t h e  only s t a t i o n with a n o t i c e a b l y d i f f e r e n t azimuth.  The  s t a t i o n a t A l b e r t Head by t h e sea and a l s o i n non-uniform topography had t h e l a r g e s t Z component. Subsequent I n v e s t i g a t i o n s by P.N.L. C o n t i n u a t i o n o f t h e r e s e a r c h i n t o s h o r t range geographical v a r i a t i o n s of the character of micropulsations has been c a r r i e d out by P.N.L. e a r t h c u r r e n t s (Cagniard  that  i 9 6 0 ) accompanying Pc's and P t ' s  might a f f e c t t h e a m p l i t u d e , of t h e magnetic v e c t o r .  I t was suspected  d i r e c t i o n , and even phase  T h i s would be p a r t i c u l a r i l y t r u e '  f o r a s t a t i o n by t h e sea o r i n mountainous t e r r a i n and i't was decided  t o c o r r e l a t e d a t a from two s t a t i o n s over  a m a g n e t i c a l l y homogeneous a r e a . Ralston i n eastern A l b e r t a .  The s i t e chosen was near  This t h e s i s Is mainly  w i t h t h e a n a l y s i s o f some o f t h e d a t a o b t a i n e d  concerned  on t h i s  investigation. Records were made o f t h e t h r e e components X, Y, and Z over t h e f r e q u e n c y  range . 0 1 t o 30 c p s . A permanent base  s t a t i o n was e s t a b l i s h e d and a mobile f i e l d  station i n a  t r u c k s e t up a t g r a d u a l l y i n c r e a s i n g d i s t a n c e s .  Both  s t a t i o n s o p e r a t e d s i m u l t a n e o u s l y w i t h t h e s i g n a l from t h e field  s t a t i o n m u l t i p l e x e d over t e l e p h o n e l i n e u s i n g s e v e r a l  c a r r i e r f r e q u e n c i e s and recorded b e s i d e t h a t from t h e base station.  Simultaneous  i n t h e magnetic  field  University of B r i t i s h  r e c o r d s were a l s o made o f v a r i a t i o n s and i n t h e a s s o c i a t e d e a r t h c u r r e n t s . Columbia  A n a l y s i s o f d a t a o b t a i n e d d u r i n g t h e I.G.Y. by s t a t i o n s throughout t h e w o r l d has been c a r r i e d out d u r i n g t h e past year.  R e s u l t s t o date (Jacobs and Sinno i960)  indicate  t h a t t h e f r e q u e n c y o f o c c u r r e n c e o f Pc's i n c r e a s e s w i t h l a t i t u d e as t h e a u r o r a l zones a r e approached.  A definite  s o l a r time dependance f o r t h e f r e q u e n c y o f o c c u r r e n c e was  found w i t h t h e maximum changing from e a r l y a f t e r n o o n  to  l a t e morning w i t h i n c r e a s i n g l a t i t u d e .  at  t h e same geomagnetic l a t i t u d e showed b o t h a l o c a l and  a u n i v e r s a l time dependance. of  Observations  The time o f maximum o c c u r r e n c e  Pc's was about 21 hours G.M.T. i n t h e n o r t h e r n  hemisphere.  The u n i v e r s a l time f a c t o r was found t o a f f e c t  the m o d u l a t i o n o f . t h e d i u r n a l o c c u r r e n c y by about 50 per c e n t .  CHAPTER I I I FIELD WORK, RALSTON ALBERTA, 1 JULY - 15 AUGUST 1959 Equipment The d e t e c t o r s f o r t h e X and Y components o f t h e magnetic f i e l d were mumetal cored and  5" i n d i a m e t e r .  s o l e n o i d s 5' i n l e n g t h  These s o l e n o i d s had 35>000 t u r n s o f  copper w i r e and a d.c, r e s i s t a n c e o f 250 ohms. The d e t e c t o r f o r t h e Z component was a 2 0 ' diameter a i r cored  shielded c o i l .  "Formel" covered 1/3  T h i s c o i l had 1100 t u r n s o f No.21  copper w i r e .  For higher frequencies o f  - 1/30 cps t h e d e t e c t o r s f o r a l l t h r e e components  were a n h y s t e r  cored  c o i l s using "Kronhite" f i l t e r s . A l l -  d e t e c t o r s were l e v e l l e d and l i g h t l y b u r i e d when i n use w i t h t h e h o r i z o n t a l component d e t e c t o r s a l i g n e d a l l y north-south  and  geographic-  east-west.  The s i g n a l s from t h e d e t e c t o r s were f e d t o a j u n c t i o n box by b u r i e d c a b l e and from t h e r e by s h i e l d e d c a b l e t o d.c.  chopper a m p l i f i e r s . The a m p l i f i e r o u t p u t s  Esterline-Angus 3/4" per minute.  drove  s t r i p - c h a r t pen r e c o r d e r s a t a speed o f When d e s i r e d t h e output from t h e  a m p l i f i e r s could a l s o be f e d i n p a r a l l e l i n t o a 6 B r u s h s t r i p - c h a r t r e c o r d e r and i n t o a 7 c h a n n e l F.R.1100 F.M. tape r e c o r d e r . although  channel  Ampex  A m p l i f i c a t i o n c o u l d be v a r i e d  i t was always n e c e s s a r y  t o g i v e t h e Z component  f o u r times t h e a m p l i f i c a t i o n g i v e n t o t h e h o r i z o n t a l components. D e t e c t o r s , a m p l i f i e r s , and r e c o r d e r s were d u p l i c a t e d at t h e mobile s t a t i o n except t h e 6 channel B r u s h and 7  FIGURE 2 (b) BLOCK DIAGRAM STATION jB RALSTON, ALBERTA  27 JULY 59  TRI FILTER  D.C. CHOPPER AMPLIFIERS COILf^M) X. C O I L j ^ ) Y. C0IL(20')Z_  120 c/s FILTER  TELEPHONE BRIDGE AMPLIFIER Y-STN.<*  (INPUT 3  MIXER  TELEPHONE BRIDGE X ,Z-STN.o4-^AMPLIFIEFf  BIXER ILTER  2.Oh k c F.M.  1.0 kc F.M. 6.25 k c F.M.  FIGURE 2 ( a ) BLOCK DIAGRAM STATION RALSTON, ALBERTA coii|>gx  D.C.  Coilf/W) Y  CHOPPER  27 J U L Y 5 9  <M>  Coil(20' )Z_I PLIFIERS A M  [= E s t e r l l n e - A n g u s R e c o r d i n g Meters  TRI FILTER  1  120  c/s Filter  6 Channel  Brush Recorder  Electric ^hrdnometer  7 Channel Tape  F.M. R e p r o d u c e Amplifier  T e l e p h o n e Yjs  Attenuator  F M Seperato Filter  T e l e p h o n e Xj> , Z J _  Attenuator  F..M. S e p e r a t 3FFilter  0  a  channel  tape r e c o r d e r .  In a d d i t i o n the m o b i l e s t a t i o n  f i l t e r i n g , a m p l i f y i n g , and for  frequency  modulating  m u l t i p l e x i n g the s i g n a l over two  the base s t a t i o n where i t was B r u s h r e c o r d e r and The  demodulated and  equipment l i n e s to fed to the  tape r e c o r d e r . (See f i g u r e 2 ) .  d e t e c t o r s f o r e a r t h c u r r e n t s were copper rods  d r i v e n i n t o moist ground and leads.  telephone  had  One  rod was  connected by t h i n copper  d r i v e n i n at the s t a t i o n , another  500* to the s o u t h , and  the t h i r d  changes i n p o t e n t i a l measured.  500' The  to the east  and  s i g n a l s were u s u a l l y  measured on a Texas I n s t r u m e n t s r e c o r d e r and o c c a s i o n a l l y on the 6 channel  Brush.  For d a i l y c a l i b r a t i o n each mumetal d e t e c t o r ( h o r i z o n t a l ) components) had  a s i n g l e c o i l around i t and  component d e t e c t o r s had within.  the 2 0 '  a 200 t u r n c o i l p l a c e d  An a.c. c u r r e n t o f . 8 1  m.a.  at .067  centrally  cps  could  be passed i n s e r i e s t h r o u g h the complete d e t e c t o r i n c l u d i n g t h a t at the m o b i l e s t a t i o n .  a field  corresponding  change o f 1Y at the h o r i z o n t a l component  d e t e c t o r s and of 1/4  Y at the v e r t i c a l component d e t e c t o r s .  Major c a l i b r a t i o n of the d e t e c t o r s was by p l a c i n g one o f the 2 0 '  carried  b r a t i o n c o i l o f 120'  circle.  diameter.  s e a r c h c o i l was  The  out  v e r t i c a l component d e t e c t o r s  around the c e n t r e o f a c i r c l e formed by an o u t e r  calibrated  system  Such a c u r r e n t would  induce a s i g n a l w i t h a peak to peak amplitude to  vertical  An i n n e r one  cali-  f o o t diameter  p l a c e d at the c e n t r e o f  c u r r e n t t h r o u g h the o u t e r c a l i b r a t i o n  the coil  -  which induced  -  16  a s i g n a l corresponding  t o a known f i e l d  change a t t h e i n n e r c a l i b r a t i o n c o i l was recorded the a m p l i t u d e detector.  as was  o f t h e s i g n a l on t h e 20' v e r t i c a l component  C a l i b r a t i o n o f t h e h o r i z o n t a l component d e t e c t o r s  was done by b u r y i n g them v e r t i c a l l y a t t h e c e n t r e o f t h e c i r c l e and n o t i n g t h e a m p l i t u d e p a s s i n g t h e recorded  o f t h e s i g n a l induced  c u r r e n t through  by  the o u t e r c a l i b r a t i o n  coil. Station  Locations  The base s t a t i o n was at s i t e cx:(50° l 6 . 5 * N , and  the mobile  l l f 08'W)  s t a t i o n moved i n t u r n t o t h r e e s i t e s a t  £ ( 5 0 ° 1 8 . 5 ' N , l l f 0 8 ' W ) , y(50°22'K, l l f 08.5'W)., and £(50°30.5'N, 110°46'W).  S t a t i o n £ was 2 m i l e s n o r t h ,  s t a t i o n V 5ir m i l e s n o r t h , and s t a t i o n £ 25 m i l e s n o r t h east o f t h e base s t a t i o n a t <* . was u n i f o r m w i t h l i t t l e  The geology o f t h e a r e a  topographic  relief.  Sediments  o f u n i f o r m t h i c k n e s s l i e above t h e g e n t l y s l o p i n g p r e cambrian basement a t a depth o f 6000 f e e t . The base s t a t i o n a t ©< was 2 m i l e s from R a l s t o n and 1 m i l e from a t r a v e l l e d r o a d . po-wer l i n e r u n n i n g i t was j o i n e d  east-west  T h e - s i t e was l e v e l w i t h a--~ 400 . y a r d s t o t h e n o r t h , where  by t h e l i n e s u p p l y i n g t h e s t a t i o n power.  S i t e s f o r the mobile f e r e n c e except t r a v e l l e d road.  s t a t i o n were w e l l c l e a r o f any i n t e r -  t h a t s i t e p was o n l y 100-yards from a Power f o r t h e mobile  s t a t i o n was s u p p l i e d  by a gas engine d r i v e n 60 c y c l e g e n e r a t o r  operated  50  -  17  -  y a r d s from the s t a t i o n and i n the o p p o s i t e d i r e c t i o n to the d e t e c t o r s .  D e t e c t o r s at b o t h the base and  s t a t i o n s were on l e v e l ground  mobile 100  at a d i s t a n c e of about  yards. F i e l d Work H i s t o r y D u r i n g t h e f i r s t two weeks o f J u l y , the base s t a t i o n was  set up at s i t e ©< , and major c a l i b r a t i o n o f equipment  carried out.  Another t e n days were r e q u i r e d t o set up  the mobile s t a t i o n at s i t e p , connect i t by telephone. l i n e to the base at s i t e o < , and t o a d j u s t the- a m p l i f y i n g r e c o r d i n g equipment.  and  By the end o f J u l y r e c o r d s were  b e i n g t a k e n at b o t h s t a t i o n s and were a l s o b e i n g m u l t i p l e x e d over t e l e p h o n e w i r e from s t a t i o n £ t o s t a t i o n ©< where the t h r e e components from each s t a t i o n were r e c o r d e d s i m u l t a n e o u s l y on magnetic tape and on the 6 c h a n n e l B r u s h . One o f the main problems was  c o r r e c t t i m i n g o f the  r e c o r d s b o t h f o r a b s o l u t e time and f o r comparison o f the s i g n a l s between two s t a t i o n s .  For the main s t a t i o n at  site<=>< the f r e q u e n c y r e g u l a t i o n o f the l o c a l power system was deemed adequate  i f o c c a s s i o n a l l y checked by r a d i o  s i g n a l s and a chronometer.  The chronometer  was w i r e d t o  p l a c e a time s i g n a l on the 7 c h a n n e l magnetic t a p e .  For  t h e m o b i l e s t a t i o n f r e q u e n t time s i g n a l s were o b t a i n e d by r a d i o and the s t r i p - c h a r t r e c o r d s marked. A was used d u r i n g p e r i o d s o f r a d i o b l a c k o u t .  chronometer When r e q u i r e d  the speed o f the engine d r i v i n g the f i e l d g e n e r a t o r c o u l d be v a r i e d .  D e s p i t e a l l e f f o r t s t h e r e was a p o s s i b l e e r r o r  - 18 of s e v e r a l seconds between i n d i v i d u a l records o f the base and mobile s t a t i o n s .  Of course  this relative  _ e r r o r d i d not apply f o r s i g n a l s multiplexed telephone  time  over the  wire.  Another d i f f i c u l t y was that s p e c i a l p r e - a m p l i f i e r s had  to be used f o r r e c o r d i n g  For  s t i l l higher  s i g n a l s around 1 - 3  cps.  f r e q u e n c i e s o f 3 - 30 cps the anhyster  rod d e t e c t o r s were r e q u i r e d .  T h i s meant that when  f r e q u e n c i e s above 1 cps were recorded from . 0 0 1 - 1 cps was not r e c e i v e d .  the broad band Also there were frequent  e r r o r s caused by the r e v e r s a l of t e r m i n a l s as the components at one s t a t i o n could be given a 180° e i t h e r to each other or to the other  phase s h i f t station.  relative  There were  even times when the s i g n a l from a e i v e n d e t e c t o r was fed to the wrong s t r i p - c h a r t record and then  incorrectly  labelled. To minimize t h i s type o f e r r o r a c o i l and b a t t e r y could be placed s i g n a l induced.  beside  each d e t e c t o r  Observation  i n t u r n and a p o s i t i v e  o f the i n d i v i d u a l  strip-chart  records would not o n l y confirm which component was being measured but would i n d i c a t e whether the s i g n a l was i n phase or 1 8 0 °  out o f phase r e l a t i v e to the other  components.  Another check was the c a l i b r a t i o n which was c a r r i e d out d a i l y during the q u i e t period i n the e a r l y evening  unless  the s i g n a l was too l a r g e f o r such c a l i b r a t i o n to be feasible.  The c a l i b r a t i o n s i g n a l with a peak to peak  amplitude corresponding  to 1 Y f o r the h o r i z o n t a l components  - 19 and  1/4  -  Y f o r the Z component could then be measured  the i n d i v i d u a l records g i v i n g  the s c a l e  constant  on  f o r that  component. E a r t h current r e c o r d s were made e i t h e r  at the base  s t a t i o n or at the mobile s t a t i o n except on a few occasions  when they were recorded  were a few  but u s u a l l y  at both s t a t i o n .  simultaneous records made of e a r t h  from the base and  short There  currents  mobile s t a t i o n on the 6 channel Brush  they were recorded  on a Texas Instruments  recorder. During was  the f i r s t  week of August the mobile  moved to s i t e / and  over telephone s i t e ¥ was  r e c o r d s were again  l i n e to the base s t a t i o n .  multiplexed The  i n o p e r a t i o n o n l y a few days and  August the mobile s t a t i o n was  station  s t a t i o n at  on the  moved to s i t e £ .  10  Because of  greater l i n e l o s s and  what appeared to be lititercapacitance  between the telephone  l i n e s o n l y one  transmitted was  at a time to the base s t a t i o n .  very weak and  ference.  component could This  showed signs of i n s t r u m e n t a l  be  signal  inter-  CHAPTER IV EVALUATION OF DATA Choice  of Records For A n a l y s i s  A l l data were kept  at P.N.L. with the r e c o r d s f o r  any g i v e n p e r i o d a v a i l a b l e on a temporary l o a n b a s i s . Therefore,  i t was decided  to work o n l y on r e c o r d s from  the 6 channel Brush where a l l three components at the base s t a t i o n at o< plus at times mobile s t a t i o n were recorded o n l y comparatively  the components from the  simultaneously.  There were  short p e r i o d s of more or l e s s  continuous  o p e r a t i o n on these r e c o r d s because o f the frequent moves of the mobile s t a t i o n .  These o p e r a t i n g p e r i o d s were  i n t e r r u p t e d when higher f r e q u e n c i e s or e a r t h c u r r e n t s were recorded  because o f the d i f f e r e n t  equipment used.  Moreover  l a r g e p a r t s o f the record were too d i s t u r b e d f o r a n a l y s i s due e i t h e r to e x c e s s i v e magnetic a c t i v i t y such as occurred  during the frequent  thunderstorms or to i n s t r u -  mental d i f f i c u l t i e s . With o n l y l i m i t e d d a t a a v a i l a b l e the study was o f necessity restricted  to the normal daytime Pc o s c i l l a t i o n s  o f 10 - 30 seconds p e r i o d .  The Z component was not used  because o f i t s n e g l i g i b l e amplitude.  There were s e v e r a l  hours o f record on 31 J u l y when the s i g n a l from s i t e jS showed almost complete c o r r e l a t i o n with that at the base s t a t i o n at©^. The envelope o f the s e r i e s o f p u l s a t i o n s s e v e r a l times  showed d i s t i n c t  p o s s i b l e beat  frequency.  "pearls" indicating a  There were s e v e r a l s e r i e s o f  o s c i l l a t i o n s at s i t e Y on 7 August which could be  - 21 c o r r e l a t e d with those at the base s t a t i o n .  The remaining  s i g n a l s studied are from the r e c o r d s on 10 August  at the  base s t a t i o n o n l y . In f i g u r e I the top two r e c o r d s are the X and Y components r e s p e c t i v e l y o f a s i g n a l at base s t a t i o n °< on 10 August  w i t h the X component showing modulation  a longer period  signal.  The t h i r d  from  record shows the  i n i t i a t i o n o f a Pc at the base s t a t i o n and the bottom record  i s o f a longer period  s i g n a l probably a  Pt w i t h  signs o f damping. Statistical  A n a l y s i s o f Data  The data s e l e c t e d on the s t r i p - c h a r t r e c o r d from the 6 channel Brush showed f a i r to good v i s u a l between components and between s t a t i o n s . no obvious phase d i f f e r e n c e s or one o f be e x p l a i n e d as a r e v e r s a l o f t e r m i n a l s .  correlation  There were e i t h e r 180° which could A plastic  template was centred over each component i n t u r n covering  the same time i n t e r v a l and the amplitude read every  f i v e seconds f o r a t o t a l o f 56 r e a d i n g s . was  No c o n s i d e r a t i o n  g i v e n to any phase d i f f e r e n c e since readings were  o n l y being taken approximately every quarter period and no c o r r e c t i o n was made f o r any constant value included due to p l a c i n g o f the template.  The amplitudes o f the  nearest c a l i b r a t i o n s i g n a l s were a l s o read and the p o s i t i v e sense o f the s i g n a l noted. A s t a t i s t i c a l a n a l y s i s was made o f each component by a u t o - c o r r e l a t i o n o f i t s s i g n a l amplitudes to o b t a i n  - 22 the dominant frequency and by c a l c u l a t i o n o f the covariance to o b t a i n the energy quency.  i n that dominant  The a u t o - c o r r e l a t i o n c o e f f i c i e n t  fre-  "r* " i s  defined as:  N-K  K  N-K  ZX-Xv* ~ J- Z X; £ Xi  =7=  -=.—V  N-K  N  1=1  \/=/v/f  N-K  Where the X i r e f e r to r e l a t i v e amplitudes  i n any  a r b i t r a r y u n i t s , N equals 56, and K has i n t e g e r values from 1 - 9 r e p r e s e n t i n g phase displacements o f 5 - 45 seconds. The c o v a r i a n c e i s d e f i n e d as the numerator o f the above e x p r e s s i o n d i v i d e d by N - K and m u l t i p l i e d appropiate c a l i b r a t i o n c o n s t a n t .  by the  The c o v a r i a n c e  corresponding to the maximum value o f TK w i l l be prop o r t i o n a l to the energy present f o r a dominant with a period corresponding  to t h i s phase  frequency  displacement.  The amplitude o f t h i s dominant frequency w i l l be prop o r t i o n a l to the square root o f the maximum value o f the c o v a r i a n c e . C a l c u l a t i o n s o f the c o r r e l a t i o n c o e f f i c i e n t s and of the c o v a r i a n c e values were made by an Alwac I I I E d i g i t a l computer at the U n i v e r s i t y o f B r i t i s h Columbia  - 23 which r e q u i r e d  a punched tape data f e e d .  An e x i s t i n g  a u t o - c o r r e l a t i o n programme had to he modified  f o r the  purpose p a r t i c u l a r l y where s c a l i n g o f the data was concerned.  The programme r e q u i r e d  to o b t a i n the r e q u i r e d  covariance  further modification values.  PHASE  SHIFT  IN SECONDS  CHAPTER V RESULTS Dominant Frequencies The a u t o - c o r r e l a t i o n c o e f f i c i e n t  r* was p l o t t e d  as a f u n c t i o n o f phase displacement i n order to compare components and to o b t a i n the dominant (See f i g u r e 3 ) .  frequencies.  Whenever the s i g n a l s f o r two s t a t i o n s  were compared a s m a l l band o f Pc's seemed to c e n t r e around the same dominant mobile s t a t i o n s .  frequency f o r both base and  Except where d i f f e r e n t  frequency s i g n a l s  occurred on the X and Y components the p l o t s o f the correlation coefficient  r*  f o r the two components were  very s i m i l a r . (See f i g u r e 4 ) . Out o f I ? s e t s o f data there were four occasions when the s i g n a l appearing on the Y component d i f f e r e d i n p e r i o d i c i t y by at l e a s t two seconds and i n one case by as much as t e n seconds from that on the X component.  Where  r e c o r d s had been obtained from both the base and mobile s t a t i o n s t h i s same d i f f e r e n c e i n p e r i o d i c i t y occurred at both s t a t i o n s ,  (See f i g u r e 5 ) .  The p e r i o d s o f the Pc's on 31 J u l y we're-16 - 18 seconds except when a longer period o f 19 - 20 seconds twice appeared on the Y component o n l y .  On 7 August the  p e r i o d s ranged from 16 - 21 seconds and on 10 August  from  19 - 29 seconds except on one o c c a s i o n when a s h o r t e r period o f 17 seconds appeared on the Y component o n l y . Maximum v a l u e s o f rk  were between .4 and . 9  with no apparent r e l a t i o n to frequency or amplitude of  es.  6  RELATIVE ENERGY COMMENCING 13 03  FOR LM.T  31  SIGNALS JULY,59  - 25 the s i g n a l .  There seemed o n l y a v e r y g e n e r a l t r e n d t h a t  the l a r g e r t h e a m p l i t u d e o f a s i g n a l t h e l a r g e r t h e maximum v a l u e o f r*  because o f a s m a l l e r p r o p o r t i o n o f  n o i s e o r s i g n a l w i t h f r e q u e n c y o u t s i d e t h e s m a l l band under c o n s i d e r a t i o n .  U s u a l l y t h e Y component had a  s m a l l e r a m p l i t u d e and hence u s u a l l y a s m a l l e r v a l u e o f r* . D i r e c t i o n and A m p l i t u d e o f The H o r i z o n t a l V e c t o r The r e l a t i v e v a l u e s o f t h e c o v a r i a n c e as s c a l e d by the computer programme were p l o t t e d as a f u n c t i o n o f phase d i s p l a c e m e n t , t h e c u r v e s r e a c h i n g a maximum a t t h e d i s p l a c e m e n t c o r r e s p o n d i n g t o t h e dominant f r e q u e n c y . (See f i g u r e 6 ) . The a m p l i t u d e o f t h e v e c t o r i s then g i v e n by:  Where^/x, x+k  andJLfy, y + k  are the values of the  c o v a r i a n c e a t t h e dominant f r e q u e n c y f o r t h e r e s p e c t i v e h o r i z o n t a l components and: _  v5< /Maximum R e l a t i v e A m p l i t u d e o f C o v a r i a n c e J  Sx i s t h e combined s c a l i n g f a c t o r from c a l i b r a t i o n and s c a l i n g f o r t h e computer, N e q u a l s t h e number o f r e a d i n g s (56),  and K i s t h e c l o s e s t i n t e g e r v a l u e t o t h e p e r i o d  d i v i d e d by f i v e .  For the data w i t h a d i f f e r e n t  frequency  s i g n a l appearing on t h e Y component, r e a d i n g s were taken at t h e average p e r i o d .  The a m p l i t u d e and d i r e c t i o n o f  340'  350'  FIG. 8  POLAR  PLOT  HORIZONTAL  Pc  RALSTON  OF VECTOR  ALBERTA  12 HR. L.M. T. STN." 31 JULY  .30 STN. B 31 JULY  STN '«• 3/ JULY  P. 2 0  STN. T 7 AUG.  STN. « - 10 AUG.  .10  P 3 2 06 00  08 0 0  F/6. 7  (0 0 0  12  00  L.M.T.  -t-  (4 0 0  (6 0 0  » 0 0  20  00  -  26 -  the r e s u l t a n t v e c t o r was then biased stronger The  i n favour o f the  component. azimuth o f the v e c t o r was c a l c u l a t e d from the  expression:  -\-  y? y+K  270  iVhere-G-is the t r u e b e a r i n g o f the v e c t o r and the a d d i t i o n o f 270° i s r e q u i r e d s i n c e the c a l i b r a t i o n and observed s i g n a l s i n d i c a t e the azimuth i s northwest. Amplitudes obtained 0.2/and  seemed to f o l l o w a d i u r n a l p a t t e r n  t h e i r peak s h o r t l y before The  were o f the order o f magnitude reaching  l o c a l noon. (See f i g u r e 7 ) .  amplitude o f the v e c t o r at s i t e P averaged 3 0 per  cent g r e a t e r than that at the base s t a t i o n ato<.  With  o n l y two case's f o r comparison the amplitude at s i t e  ^  was o n l y 2 0 per cent g r e a t e r than that at the base s t a t i o n although The  s i t e Y was twice the d i s t a n c e o f s i t e jB . p o l a r p l o t o f the h o r i z o n t a l v e c t o r i n d i c a t e s  that the d i u r n a l p a t t e r n i s a c l o s e d f i g u r e with the maximum e x c u r s i o n t a k i n g p l a c e during d a y l i g h t hours (See f i g u r e 8 ) .  caused mostly by changes i n amplitudes The  azimuths are n o r t h w e s t e r l y ,  more n o r t h e r l y , t h a n those  those  at s i t e P  being  at the base s t a t i o n a t o ( .  T h i s a r i s e s because the g r e a t e r amplitude at the mobile s t a t i o n i s due to a l a r g e r X component.  The d i r e c t i o n  of motion o f the d i u r n a l p a t t e r n i s a n t i - c l o c k w i s e on 1 0 August when the d i r e c t i o n i s r e v e r s e d .  except  CHAPTER VI CONCLUSIONS The normal daytime Pc o s c i l l a t i o n s with p e r i o d from 10 - 30 seconds seem to occur i n a s m a l l frequency band centred around one dominant frequency. s i g n a l may  two  observed  be made up of two or more small bands of  Pc's with some i n s t r u m e n t a l n o i s e and amplitude  The  possibly  low  Pc of a d i f f e r e n t dominant frequency.  such s m a l l bands of Pc's with d i f f e r e n t  f r e q u e n c i e s and widely separated  e q u i v a l e n t amplitudes azimuths.  On  may  At  times  dominant  occur with  such o c c a s i o n s the X  component has one dominant frequency and  the Y component  another. Beats  should occur when two  Pc's of d i f f e r e n t  frequency but e q u i v a l e n t amplitude signal.  Pearls indicating  are present i n the  such beats occurred on s e v e r a l  o c c a s s i o n s on the record f o r the 31 J u l y i n c l u d i n g  two  s e t s of data when there were d i f f e r e n t dominant f r e q u e n c i e s on the X and Y components. caused  by two  s i g n a l s b e a t i n g with a d i f f e r e n c e i n  period of a few The  These p e a r l s could have been  seconds.  h o r i z o n t a l v e c t o r seems to f o l l o w a c l o s e d  d i u r n a l p a t t e r n w i t h the g r e a t e s t e x c u r s i o n s o c c u r r i n g during d a y l i g h t hours. be reached  The maximum amplitude  seems to  s h o r t l y before l o c a l noon.  I n i t i a t i o n of a s i g n a l at two by a few m i l e s i s simultaneous a h i g h c o r r e l a t i o n except  and  stations  separated  the s i g n a l s show  f o r d i f f e r e n c e s i n amplitude  - 28 and  azimuth of the h o r i z o n t a l v e c t o r .  averaged  The  amplitude  30 per cent g r e a t e r f o r a s t a t i o n 2 m i l e s n o r t h  o f the base s t a t i o n although  i t seemed to be o n l y 2G  per cent g r e a t e r f o r a s t a t i o n 5 h m i l e s n o r t h o f the base.  There i s no obvious  d i f f e r e n c e i n amplitude  explanation for t h i s  s i n c e any l a t i t u d e  should- i n c r e a s e w i t h d i s t a n c e and p r e c l u d e s any d i f f e r e n c e due currents.  The  effect  the uniform  geology  to changes i n the e a r t h  s m a l l e f f e c t on the t o t a l v e c t o r o f  the a s s o c i a t e d e a r t h c u r r e n t s i s a l s o evident i n the n e g l i g i b l e Z component. The  s t a t i s t i c a l a n a l y s i s of the data gave  factory results.  I f amplitudes  could be read  satiselect-  r o n i c a l l y p o s s i b l y by i n c l u d i n g the data on magnetic tape then g r e a t e r accuracy would be o b t a i n e d .  This  would permit more exact d e t e r m i n a t i o n of the dominant frequency, vector.  and o f the amplitude  When Pc's of d i f f e r e n t  and  azimuth of the  frequency occur,  should then be p o s s i b l e to r e s o l v e the s i g n a l s two  v e c t o r s with d i f f e r e n t  different  it into  p e r i o d s and p o s s i b l y  azimuths.  There i s a need f o r simultaneous s t a t i o n s over a long time d a t a i s obtained  interval.  r e c o r d s from Only a f t e r  should the d i s t a n c e between the  s t a t i o n s be i n c r e a s e d .  two  sufficient two  - 29 BIBLIOGRAPHY Bennett,  W.H.  Cagniard,  L . 1956.  (Springer  Verlog,  Duffus, Duffus,  195'8.  195U.  a n d H u l b u r t , E.O.  Handbuch  Phys.  Rev.  Vol.^7,  derPhysic,  95,315.  P. +07- +69 l  Berlin).  H.J. and Shand,  J.A.  1958. C a n .  H . J . , N a s m y t h , P.W. , S h a n d , N a t u r e , 1.81, 1258.  36,508.  J . Phys.,  J.A., and W r i g h t , C . S .  D u f f u s , H . J . , S h a n d , J . A . , W r i g h t , C . S . , Nasmyth, a n d J a c o b s , J . A . 1959. J . G e o p h y s . 6k, 581. "" Goldberg,  P.A. 1956.  Jacobs, J.A. (in press).  l  i960.  Nature, Phys.  177,  P.W.,  1219.  5.  a n d Chem. o f E a r t h s V o l .  J a c o b s , J . A . a n d S i n n o , K. 65, 1 0 7 .  I960.  K a t o , Y . a n d A k a s o f u , S. 1957. Ser. 5, G e o p h y s . 7, N o . 2. K a t o , Y. a n d W a t a n a b e , T . 1957. Ser. 5, G e o p h y s . 8, N o . 2.  J . Geophys.  S c i . Repts.,  Tohoku  S c i . Repts.,  J.A.. 1^58.  O b a y a s h i , T. a n d J a c o b s , A s t r o . Soc-.-.,T1, <H.  Georhys.  S h a n d , J . A . , W r i g h t ^ C . S . 'j a n d : D u f f u s , - H . J . N a v a l - L a b . , D.R .B j R e p t -15. ?  Research  Univ.,  Tohoku  Univ.,  J . , Rcy.  1959.  Pacific  y  Terada,  J . 1917.  T r o i t s k a y a , V.A. Translation W + R ,  College  S c i . , Tokyo,  Defence  37,  No. o.  Research Board 1  (Canada)  T r o i t s k a y a , . , V . A . 1957. Abstracts of t h eReports XI G e n e r a l Assembly o f t h e I . U . G . G . , p. 20. :  atthe  

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