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Prompt world-wide geomagnetic effects of high-latitude nuclear explosions Caner, Bernard 1964

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PROMPT WORLD-WIDE GEOMAGNETIC EFFECTS OF HIGH-ALTITUDE NUCLEAR EXPLOSIONS by BERNARD CANER B.Sc,  U n i v e r s i t y of A l b e r t a ,  i960  A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE i n the Department of GEOPHYSICS  We accept t h i s t h e s i s as conforming required  t o the  standard  THE UNIVERSITY OF BRITISH COLUMBIA March, 1964  In presenting  t h i s t h e s i s i n p a r t i a l f u l f i l m e n t of  the requirements for an advanced degree at the U n i v e r s i t y of • B r i t i s h Columbia, I agree that a v a i l a b l e f o r reference  and  the L i b r a r y shall'make i t f r e e l y  study,  I f u r t h e r agree that  per-  m i s s i o n f o r extensive copying- of t h i s t h e s i s f o r s c h o l a r l y purposes may  be granted by the Head of my Department or  his representatives.  I t i s understood that;copying or p u b l i -  c a t i o n of t h i s t h e s i s f o r f i n a n c i a l gain shall, not without my  written  Department of  permission*  GEOPHYSICS  The U n i v e r s i t y of B r i t i s h Columbia, Vancouver 8, Canada Date  by  be  allowed  i  ABSTRACT  A b r i e f summary of o b s e r v a t i o n a l data i s presented, c o v e r i n g the d i s t u r b a n c e s recorded w i t h i n seconds of h i g h a l t i t u d e n u c l e a r d e t o n a t i o n s , with p a r t i c u l a r emphasis on the "phase B"  s i g n a l recorded at H+2  " S t a r f i s h " t e s t of J u l y 9 ,  1962.  seconds f o l l o w i n g the  The  i s t i c s of t h i s s i g n a l are s p e c i f i e d ,  salient character-  and a number of  suggested models are analysed i n d e t a i l .  Although no  con-  c l u s i v e d e c i s i o n can be reached on the b a s i s of p r e s e n t l y a v a i l a b l e data, the most l i k e l y mechanism appears  t o be  hydromagnetic waves along the f i e l d l i n e through the a t i o n p o i n t , with energy  deton-  conversion i n t o electromagnetic  modes at the m i r r o r p o i n t s .  V  ACKNOWLEDGEMENTS  Work on t h i s r e p o r t was begun a t V i c t o r i a Observatory  (Dominion A s t r o p h y s i c a l O b s e r v a t o r y ) .  Magnetic I should  l i k e t o thank P r o f . J.A. Jacobs f o r p r o v i d i n g the f a c i l i t i e s f o r i t s completion.  V a l u a b l e suggestions and c r i t i c i s m  have been r e c e i v e d from P r o f . T. Watanabe of the Department of Geophysics,  U n i v e r s i t y o f B r i t i s h Columbia, Dr. K. Whitham  of the Dominion Observatory,  and Dr. J.P. Kenney and Dr.  H.R. W i l l a r d of the Boeing S c i e n t i f i c Research L a b o r a t o r i e s . I should l i k e t o thank the D i r e c t o r of the S i g n a l s Research  and Development E s t a b l i s h m e n t  (U.K. M i n i s t r y of  A v i a t i o n ) , and Dr. C.P. S e c h r i s t of HRB-Singer Inc., f o r s u p p l y i n g unpublished  data.  ii  TABLE OP CONTENTS  ABSTRACT  i  TABLE OP CONTENTS  i i  LIST OF FIGURES  iv  ACKNOWLEDGEMENTS  v  INTRODUCTION  1  OBSERVATIONAL DATA  4 14  INTERPRETATION - "PHASE A"  , . . . . 15  INTERPRETATION - "PHASE B" . . . "PHASE B" - DIRECT EFFECT MODELS 1)  Hydromagnetic waves i n Ionosphere  19  2)  Hydromagnetic waves i n h i g h a l t i t u d e ducts . . . . 20  3)  Neutron-decay  4)  F i s s i o n - p r o d u c t betas  5)  S e t t i n g up of l o c a l c o n d i t i o n s  21  betas  24 . . .  25  "PHASE B" - SECONDARY FOCUS MODELS General comments . .  26  1)  Neutron-decay  28  2)  F i s s i o n - p r o d u c t betas  3)  Hydromagnetic-Electromagnetic i n the lower ionosphere  betas  29 conversion 30  iii  4)  Hydromagnetic impulse guided along .33  the f i e l d - l i n e 5)  Hydromagnetic wave along the f i e l d - l i n e  38  6)  Protons guided along the f i e l d - l i n e  40 44  CONCLUSION APPENDIX I - ADDITIONAL LINES OF APPROACH  . . . .' . .  APPENDIX I I - X-RAY IONIZATION AND ALFVEN VELOCITIES BELOW THE DETONATION POINT . REFERENCES  .45  51 59  iv  LIST OF FIGURES  Fig. 1  Geomagnetic r e c o r d i n g at V i c t o r i a ,  J u l y 9, 1962, Fig. 2  0900-0901 UT College,  0859:50-0900:45 UT  8  Geomagnetic r e c o r d i n g at C h r i s t c h u r c h , England, J u l y 9,  Fig. 4  7  Geomagnetic r e c o r d i n g at State  .Pa., J u l y 9, 1962, Fig. 3  B.C.,  1962, 0900:09-0900:26  UT  Frequency-response c h a r a c t e r i s t i c s of instrumentation  used at V i c t o r i a ,  State 10  C o l l e g e , and C h r i s t c h u r c h Fig. 5  9  Summary of geomagnetic r e c o r d i n g s from Argus I I I ( a f t e r B e r t h o l d , H a r r i s and  Hope, i960) Fig. 6  17  F i e l d l i n e through the d e t o n a t i o n " S t a r f i s h " t e s t of J u l y 9,  point -  1962  34  Fig. 7  Energy spectrum of f i s s i o n neutrons  4l  Pig. 8  x-Ray i o n i z a t i o n below the d e t o n a t i o n p o i n t  54  Fig. 9  A l f v e n v e l o c i t i e s below the d e t o n a t i o n  55  point  INTRODUCTION  T h i s r e p o r t examines i n d e t a i l one narrow aspect of geomagnetic d i s t u r b a n c e s set up by h i g h - a l t i t u d e n u c l e a r t e s t s - the world-wide s i g n a l s recorded w i t h i n a few  seconds  of  oscil-  d e t o n a t i o n , with p a r t i c u l a r emphasis on the major  l a t o r y s i g n a l , the s t a r t of which was  recorded at many  l o c a t i o n s about 2 seconds a f t e r the d e t o n a t i o n , and which we have d e s i g n a t e d "phase B".  Slower geomagnetic a r r i v a l s  as  w e l l as r a d i o p r o p a g a t i o n e f f e c t s have been r e p o r t e d  and  analysed by s e v e r a l observers  alia,  1964).  Although  ( f o r example, Maeda e t  a l l these e f f e c t s are o b v i o u s l y r e l a t e d i n  as f a r as the source i s concerned,  the a c t u a l mechanisms  i n v o l v e d appear to be e n t i r e l y d i f f e r e n t , thus the separate treatment "phase B"  justifying  of an i s o l a t e d f e a t u r e such as the  signal. The main i n t e r e s t of t h i s s i g n a l l i e s i n i t s  - broad  s i m i l a r i t y with c e r t a i n types of n a t u r a l geomagnetic  p u l s a t i o n s ( p e a r l s , or type-A o s c i l l a t i o n s ) . advantage of a c o n t r o l l e d source  Having the  (at l e a s t In time  and  l o c a t i o n ) , i t t h e r e f o r e p r o v i d e s an i n t e r e s t i n g o p p o r t u n i t y for  complementing the study of p o s s i b l e n a t u r a l m i c r o p u l -  s a t i o n mechanisms - even though the analogy  with n a t u r a l  phenomena can o n l y be f o l l o w e d to a l i m i t e d  extent.  Although no e x p l i c i t c o n c l u s i o n s are drawn i n t h i s r e s p e c t ,  2.  the proposed mechanisms have been narrowed down to essenti a l l y the same as those which are b e i n g c o n s i d e r e d  as  explanations f o r pearl-type micropulsations. T h i s r e p o r t w i l l be l i m i t e d to a d i s c u s s i o n of g l o b a l geomagnetic e f f e c t s recorded w i t h i n a few  seconds of  the d e t o n a t i o n ,  local  and i t w i l l not i n c l u d e i s o l a t e d  e f f e c t s i n the v i c i n i t y areas.  The  of the launch zones or  o b s e r v a t i o n a l data w i l l f i r s t be  fairly briefly.  conjugate presented  A number of p o s s i b l e mechanisms w i l l  then  be c o n s i d e r e d on a q u a l i t a t i v e b a s i s , with rough o r d e r - o f magnitude q u a n t i t a t i v e support.  I t should be mentioned at  the o u t s e t t h a t no f u l l y acceptable unique s o l u t i o n I s proposed.  In p a r t i c u l a r ,  t h e o r e t i c a l work i s r e q u i r e d on  hydromagnetic-electromagnetic frequencies.  energy c o n v e r s i o n at very  low  However, t h i s i n v e s t i g a t i o n should p r o v i d e  a  u s e f u l b a s i s f o r more d e t a i l e d work on any p a r t i c u l a r mechanism.  I n view of the l a r g e r e l e a s e of energy i n v a r i o u s  forms, a unique s o l u t i o n may of  not be p o s s i b l e on the b a s i s  the p r e s e n t l y a v a i l a b l e data,  s e v e r a l d i f f e r e n t mechanisms may The  energy output  J o u l e s per K i l o t o n .  s i n c e combinations of be i n v o l v e d .  of a n u c l e a r e x p l o s i o n i s  F o r an u n s h i e l d e d f i s s i o n  105  explosion i n  space t h i s i s d i s t r i b u t e d roughly as f o l l o w i n g (Glasstone,  1963; L a t t e r and L e L e v i e r , 1964): x-rays  (1  to a few Kev  Approximately  30-70$ i n  energy range), 0.01-1$ i n prompt  7-rays (mean energy about 1 Mev), ( 0.1 Mev  to a few Mev),  0.1-1$ In prompt neutrons  and the remainder i n k i n e t i c  of f i s s i o n products, w i t h a few percent i n d e l a y e d  energy  radiation.  4.  OBSERVATIONAL DATA  The r e l e v a n t t e s t s f o r which i n f o r m a t i o n i s a v a i l able are the f o l l o w i n g : Aug. 1958:  two t e s t s I n the P a c i f i c above Johnston I s l a n d ,  "Teak" a t an a l t i t u d e o f 70-80 km, "Orange" at 30-40 km. The announced  y i e l d was " i n the Megaton range".  Sowle  (1961) e s t i m a t e d the y i e l d as about 4 Megatons f o r "Teak" and 2-4 Megatons f o r "Orange". Aug.-Sept.  1958:  three l o w - y i e l d (1-2  Kilotons) explosions  over the South A t l a n t i c , code-named Argus I, I I and I I I , a t a l t i t u d e s of about 480 km. J u l y 9, 1962:  Johnston I s l a n d , y i e l d e s t i m a t e d at  1.4  Megatons, a l t i t u d e 400 km, code name " S t a r f i s h " . Oct. 20, Oct. 26, Nov. 1,  1962:  low and medium a l t i t u d e  ("tens o f k i l o m e t e r s " ) t e s t s , with sub-megaton y i e l d s . None of the lower a l t i t u d e produced major g l o b a l geomagnetic produced both f a s t 1959)  (under 100 km) t e s t s  effects.  Most of them  (onset time w i t h i n 1 second - McNish,  and slower f o l l o w i n g bay-type d i s t u r b a n c e s a t l o c a t i o n s  w i t h i n about 1000-2000 km o f the launch area, f a l l i n g o f f r a p i d l y with distance.  Some sharp e f f e c t s were a l s o  observed at the conjugate p o i n t s .  Lawrie, Gerard, G i l l  (1959) and Obayashi (1963) have summarized and i n t e r p r e t e d these e f f e c t s . observed,  However, no major world-wide e f f e c t s were  i n s p i t e of the h i g h y i e l d s . F o r the h i g h e r - a l t i t u d e Argus t e s t s , e f f e c t s were  observed  at magnetic s t a t i o n s at w i d e l y separated l o c a t i o n s  (Eschenbrenner Amplitudes  et a l i a ,  i 9 6 0 ) , i n s p i t e of the low y i e l d s .  were very small ( f r a c t i o n to a few gammas),  and  r e c o r d i n g s were o b t a i n e d o n l y on s e n s i t i v e equipment - i n some cases b a r e l y above the background l e v e l .  Berthold,  H a r r i s and Hope (i960) have summarized t h i s data i n d e t a i l f o r Argus I I I (Sept. 6,  1958).  The  a r r i v a l times were  p l o t t e d a g a i n s t s t a t i o n to d e t o n a t i o n p o i n t d i s t a n c e s . slope of a s t r a i g h t l i n e f i t t e d to the f i r s t  The  a r r i v a l points  i n d i c a t e d a g r o u n d - l e v e l p r o p a g a t i o n v e l o c i t y of 3050 km/sec. No probable e r r o r was  specified for this  result.  S i m i l a r g l o b a l e f f e c t s were recorded f o l l o w i n g the " S t a r f i s h " t e s t of J u l y 9, h i g h e r amplitudes t e s t was  1962,  but with c o n s i d e r a b l y  - presumably due  to the h i g h e r y i e l d .  The  announced w e l l i n advance, and a countdown t r a n s -  m i t t e r c o u l d be monitored.  Nevertheless,  a surprisingly  small amount of h i g h - q u a l i t y u n c l a s s i f i e d data has been c o l l e c t e d i n geomagnetism. v e r y few  With a few n o t a b l e  exceptions  s t a t i o n s improved t h e i r o p e r a t i n g techniques f o r  t h i s p a r t i c u l a r p e r i o d i n order to o b t a i n t i m i n g a c c u r a c i e s of ±0.1  seconds o r b e t t e r ( i n p a r t i c u l a r accurate  absolute  t i m i n g on the r e c o r d i t s e l f and speed-up o f r e c o r d e r s ) . A l s o , the hour time-mark o b l i t e r a t e d the f i r s t a r r i v a l a t many l o c a t i o n s , p a r t i c u l a r l y on slow-speed magnetograms. Finally,  the amplitude of the s i g n a l s was unexpectedly  large.  At almost a l l l o c a t i o n s the instrument  settings  were too s e n s i t i v e and the t r a c e s went o f f - s c a l e . sequently  very l i t t l e  Con-  v a l i d amplitude data has so f a r be-  come a v a i l a b l e , and t h i s r e p o r t i s based almost e n t i r e l y on t i m i n g c o n s i d e r a t i o n s , p a r t i c u l a r l y from the 4 f o l l o w i n g stations: V i c t o r i a , B.C., Canada - Dominion  Observatory  C o l l e g e , A l a s k a - U n i v e r s i t y of A l a s k a State C o l l e g e , Pa., U.S.A. - HUB S i n g e r I n c . C h r i s t c h u r c h , England - S i g n a l s Research and Development Establishment The  C h r i s t c h u r c h data were p a r t i c u l a r l y  valuable  In view of the l o n g d i s t a n c e coverage, and i n view of the h i g h q u a l i t y o f the a v a i l a b l e r e c o r d i n g s - complete  three-  c o m p o n e n t s e t s o f high-speed h i g h - s e n s i t i v i t y as w e l l as v  broad-band l o w e r - s e n s i t i v i t y r e c o r d i n g s .  F i g u r e s 1,  3 show the high-speed r e c o r d i n g s f o r V i c t o r i a , and C h r i s t c h u r c h , and F i g u r e 4 the frequency i n s t r u m e n t a t i o n used. i s summarized i n Table  State  2 and College  response of the  The r e l e v a n t data f o r the 4 s t a t i o n s 1 below.  the f o l l o w i n g i n f o r m a t i o n :  Consecutive  l i n e s contain  a) great c i r c l e d i s t a n c e  (km) t o  Johnston I s l a n d ; b) d e l a y time (seconds) f o r the f i r s t  arrival.  FIG. I  VICTORIA  MAGNETIC  DECLINATION  OBSERVATORY  (MAGNETIC  E-W)  0.5 GAMMA/DIVISION  0900  0900:11.4  0900:30  UNIVERSAL TIME STATE COLLEGE, PENNSYLVANIA FIG. Z - GEOMAGNETIC MICROPULSATIONS - 9 JULY 1962 (HORIZONTAL COMPONENT) AFTER COURTESY  SECHRIST (1962) HRB-SINGER  INC.  FIG. 3  CHRISTCHURCH, ENGLAND  COURTESY SRDE  2  3r  UJ  CO U.  1.0  O  Hi  co  v  0.5  o a. CO ui a: a  a.  CHRIS CHUFlCHx,  si-/;  0.1  COLLEGE  V  > a:  1  o  0.05  UJ  -J UJ  I —  0.0!  0.001  0.01  0.1 FREQUENCY  10  (CPS)  FIG. 4 MAGNETOMETER CHARACTERISTICS: VICTORIA, STATE COLLEGE, CHRISTCHURCH  11.  The d e t o n a t i o n time  (H=0) i s 0 9 0 0 : 0 9 . 0 2 5 ± 0 . 0 2 5 sees, as  deduced from the sharp c u t - o f f o f the countdown t r a n s m i t t e r and o t h e r recorded r a d i o e f f e c t s  (Hanley, 1962 ; Caner and  Whitham, 1962); c ) probable and maximum e r r o r s f o r the d e l a y time - the l a t t e r i n c l u d e s the u n c e r t a i n t y i n o r i g i n d) components recorded, and e s t i m a t e d peak-to-peak  time;  amplitude  ( i n gammas) o f the f i r s t movements ( a l l o f f - s c a l e ) ; e) r e f e r e n c e .  TABLE 1  Victoria  College  State C o l l e g e  5400  5600  9600  12000  2.0  2.1  2.4  1.94  ±0.06 ( 0 . 1 )  ±0.1 (0.3)  ±0.01  ±0.1  (0.2)  D >20  P  >5  NS >10  Christchurch  (0.04)  EW  >10-15  NS  > 5  Z <0.5 Caner and Whitham (1962)  Wilson and Suglura (1963)  Sechrist (1962)  Stevens (unpublished)  12.  An important  group of o b s e r v a t i o n s comes from the  network o f the U.S. Army E l e c t r o n i c s Research and Development laboratory.  These have not been p u b l i s h e d , but a summary of  the r e s u l t s was presented I n a paper a t the IUGG meeting (Bomke e t a l i a ,  1963).  corded a t H+1.9  seconds s i m u l t a n e o u s l y a t a l l the s t a t i o n s  A s t r o n g o s c i l l a t o r y s i g n a l was r e -  of t h i s network ( F l o r i d a , Maine, South C a r o l i n a , New J e r s e y as w e l l as Hawaii and Samoa).  No probable e r r o r was g i v e n  f o r t h i s f i g u r e ; ±0.1 seconds i s p r o b a b l y a reasonable estimate. quencies  A sharp broad-band p u l s e c o n t a i n i n g h i g h e r f r e (but of much lower amplitude)  was recorded a t the  i n s t a n t o f d e t o n a t i o n a t Samoa and Hawaii. A t h i r d group of o b s e r v a t i o n s comes from the network o f the " I n s t i t u t de Physique  du Globe" o f the U n i v e r -  s i t y of P a r i s (Roquet, S c h l i c h and S e l z e r , 1962). the s t a t i o n s , Chambon-la-Foret i n France  Two of  and Kerguelen i n  the I n d i a n Ocean, r e p o r t e d the instantaneous a r r i v a l a t H+0 (±0.1 t o ±0.2 seconds), sharp reinforcement 2 seconds l a t e r  f o l l o w e d by a v e r y s t r o n g and  of the p e r t u r b a t i o n a t Chambon about  (Roquet e t a l i a ,  1963).  The t h i r d  station,  Dumont d ' U r v i l l e i n the A n t a r c t i c , r e p o r t e d a major a r r i v a l at H+2 ± 1.5  seconds.  F i n a l l y , h i g h - r e s o l u t i o n ELF r e c o r d i n g s o b t a i n e d at Byrd i n the A n t a r c t i c at Westford,  (Lokken, p r i v a t e communication) and  Mass. ( B a l s e r and Wagner, 1963) show both the  13.  i n s t a n t a n e o u s p u l s e and the higher-amplitude, s i g n a l at H+2, signals.  lower-frequency  w i t h d i s t i n c t s e p a r a t i o n between the  two  Because of the high-frequency passbands of these  systems ( 5 - 3 5 cps f o r Westford,  2-30 cps f o r Byrd) no  c l u s i o n s can be drawn r e g a r d i n g the waveform of the  con-  second  s i g n a l on these r e c o r d i n g s . There are many o t h e r r e c o r d i n g s , but s i n c e a b s o l u t e t i m i n g a c c u r a c i e s are ± 0 . 5 to ± a few  seconds  they do not  add  any u s e f u l i n f o r m a t i o n from the p o i n t of view of t i m i n g although they are important f o r an examination of geographic coverage. (1963) We  As p o i n t e d out by Roquet, S c h l i c h and  the evidence f o r g l o b a l synchronism  can i d e n t i f y the f o l l o w i n g d i s t i n c t  "phase A":  Selzer  i s overwhelming.  effects:  an i n s t a n t a n e o u s p u l s e , low-amplitude,  frequency content (> 2 c p s ) , at H+0  high-  (± m i l l i s e c o n d s to ± 0 . 1  seconds). "phase B": H+2  a second, major o s c i l l a t o r y s i g n a l s t a r t i n g at  s i m u l t a n e o u s l y ( ± 0 . 1 to 0 . 2 sees) a l l over the globe.  The p e r i o d i s i n i t i a l l y to  decrease t o about  about  2-2.5  3 . 5 t o 4 seconds,  seconds by the f i f t h  T h i s p e r i o d decrease i s not d e f i n i t e l y proved,  and  appears  oscillation. s i n c e at most  s t a t i o n s the t r a c e s went o f f - s c a l e and the zero r e f e r e n c e shifted.  In view of the r a p i d amplitude decay a r e l i a b l e  frequency measurement becomes  difficult.  14.  PHASE A - INTERPRETATION  I n t e r p r e t a t i o n of the "phase A" s i g n a l does not present any p a r t i c u l a r d i f f i c u l t i e s ;  there are two  possible  mechanisms: a)  a s p h e r i c , presumably  e x c i t e d by the prompt 7-ray  e m i s s i o n (which occurs w i t h i n microseconds of  i t s energy at a l t i t u d e s of about  by e l e c t r o s t a t i c  and d e p o s i t s most  2 0 - 3 0 km),  (charge s e p a r a t i o n ) e f f e c t s . >  or p o s s i b l y I t i s prob-  a b l y r e i n f o r c e d by Schumann o s c i l l a t i o n s of the e a r t h ionosphere c a v i t y .  T h i s i s confirmed by the Byrd ELF r e -  c o r d i n g which has e x c e l l e n t time r e s o l u t i o n - the  fundamental  Schumann frequency can be c l e a r l y i d e n t i f i e d on the f i r s t s i g n a l (Lokken, p r i v a t e communcation).  The f i r s t s i g n a l on  the Westford ELF r e c o r d i n g i s r e p o r t e d to be s i m i l a r t o t h a t observed f o r l i g h t n i n g s t r o k e s ( B a l s e r and Wagner, 1 9 6 3 ) . b)  the second p o s s i b l e mechanism i s e f f e c t s of neutron-  decay b e t a s .  T h i s w i l l be d i s c u s s e d i n more d e t a i l at a  l a t e r stage. The  reason why  not a l l s t a t i o n s recorded the  "phase A" s i g n a l i s almost c e r t a i n l y a combination of i n s t r u mental l i m i t a t i o n s and r a p i d amplitude f a l l - o f f distance.  with  The frequency response of most of the d e t e c t o r s  used f a l l s o f f very r a p i d l y beyond a few cps; f o r example the 3 db high-frequency c u t - o f f p o i n t s f o r V i c t o r i a , State  15.  C o l l e g e and C h r i s t c h u r c h (broadband cps and 2 cps r e s p e c t i v e l y ,  r e c o r d ) are 5 cps, 1.5  A very low-amplitude  s i g n a l at  8 cps would t h e r e f o r e be masked by background a c t i v i t y and/or instrument n o i s e , whereas i t shows up on r e c o r d s o b t a i n e d e i t h e r at c l o s e l o c a t i o n s (Hawaii, Samoa), o r with  special-  i z e d ELP equipment (Byrd, Westford)., o r with low-noise h i g h frequency s e n s i t i v e equipment such as t h a t used by the French network.  PHASE B - INTERPRETATION  I n t e r p r e t a t i o n of the "phase B" s i g n a l i s f a r more complicated and c o n t r o v e r s i a l . of  The s a l i e n t  t h i s s i g n a l are summarized below, and any suggested mech-  anism must take these p o i n t s i n t o a)  characteristics  g l o b a l synchronism  (±0.1-0.2  account: sees)  b) . 2 second d e l a y a f t e r e x p l o s i o n ( ± 0 . 1 - 0 . 2  sees)  (over 2 0 - 3 0 gamma/sec)  c)  extremely sharp r i s e  d)  i n i t i a l p e r i o d 3 . 5 - 4 sees ( i . e . frequency 0 . 2 8 - 0 . 2 5 cps)  e)  amplitude h e a v i l y damped  f)  large i n i t i a l  g)  altitude-dependence  amplitude  (about 3 0 - 5 0 gamma)  (occurs o n l y when the source i s  above F l a y e r ) h)  d e c r e a s i n g p e r i o d , t o about  2 - 2 . 5 sees (?)  16.  Before  beginning  a d i s c u s s i o n of p o s s i b l e mech-  anisms, i t i s u s e f u l to r e c o n s i d e r the Argus I I I data  to  check whether i t c o u l d f i t some of the above c h a r a c t e r i s t i c s . The  r e l e v a n t f i g u r e from B e r t h o l d et a l i a  duced i n F i g u r e 5«  I f we  (i960) i s repro-  v i s u a l i z e the f u l l v e r t i c a l s c a l e  ( i . e . extended to zero d i s t a n c e ) i t becomes obvious t h a t the slope of a l i n e based on a number of p o i n t s bunched over a narrow range i s extremely s e n s i t i v e to e r r o r s i n i n d i v i d u a l point positions.  The  Azores o b s e r v a t i o n i s not  very  r e l i a b l e - to quote from Newman's (1959) o r i g i n a l paper: "there may  be a s i g n a l between p l u s 4 and p l u s 6 seconds".  T h i s l e a v e s 5 p o i n t s , a l l i n the range 12000 - 13700 i.e. ing  c o v e r i n g o n l y about 15$ of the t o t a l range. the probable  km,  Consider-  e r r o r s of some of the o b s e r v a t i o n s , i t  becomes obvious t h a t any  slope d e r i v e d on t h i s b a s i s i s not  too r e l i a b l e .  i t can be c l e a r l y seen t h a t a v e r -  t i c a l line  In f a c t ,  ( I . e . g l o b a l synchronism) would f i t the data  as w e l l or b e t t e r (see dotted, l i n e on F i g u r e 5 ) . strengthened  by T r o i t s k a y a ( 1 9 6 1 ) ,  a r r i v a l s recorded  who  This i s  reported that  at the S o v i e t t e l l u r i c  stations  the  (extending  over 1 2 0 ° i n l o n g i t u d e ) were simultaneous to w i t h i n 1 The  just  second.  exact d e l a y time i s u n f o r t u n a t e l y not known, s i n c e the  e f f e c t i v e o r i g i n time has not been p u b l i s h e d .  I t would be  very i n t e r e s t i n g to know whether the d e l a y i s of the  order  of 2 seconds a l s o , or whether i t i s dependent on y i e l d altitude.  I t i s not c l e a r whether the papers by  and  Berthold  9.800  AZORES  430 3050 ^KM/SEC" KM/SEC ( KM/SEC  2t  I  UJ  o  NEW JERSEY MAINE  ? I2,000f^ 5 12.200 J 12.500  UPPSALA  12.9001  {  REYKJAVIK  SUGGESTED ALTERNATIVE  13.700 .-•-H  o  W^ - ARIZONA 1  r  10  . 1 ..... I  .'.J  I.  20 30 40 50 TIME AFTER ZERO. SECONDS  FIG. 5 Replotted recordings, giving an indication of velocities of two signals from Argus III. AFTER BERTHOLD, HARRIS, HOPE (I960)  18.  et a l i a  ( i 9 6 0 ) and Bomke e t a l i a  to unpublished was  ( i 9 6 0 ) were based on  access  o r i g i n time data, or whether the o r i g i n  d e r i v e d from e x t r a p o l a t i o n of the d i s t a n c e - t i m e  for later arrivals.  time  lines  In the l a t t e r case, the same o b j e c t i o n s  apply as p r e v i o u s l y d i s c u s s e d f o r the 3050 km/sec  velocity,  and the o r i g i n time can be c o n s i d e r e d unknown to  ±2 sees,  i . e . a 2 second d e l a y i s p o s s i b l e .  However, i f these  papers were based on access to r e l i a b l e o r i g i n i n f o r m a t i o n (which i s a l i k e l y assumption), data i s about 4 ± 0 . 5  seconds.  the d e l a y i n d i c a t e d by  T r o i t s k a y a ( i 9 6 0 ) reached  s i m i l a r t e n t a t i v e c o n c l u s i o n , based on the time between a f i r s t  impulse-type  the second ( o s c i l l a t o r y )  the a  spacing  a r r i v a l (assumed at H+0)  and  signal.  A number of d i f f e r e n t mechanisms w i l l now  be  dis-  cussed i n d e t a i l ; some of these are o b v i o u s l y u n s u i t a b l e to e x p l a i n the "phase B" another briefly.  s i g n a l , but s i n c e at one  time  or  they have been c o n s i d e r e d , we have i n c l u d e d them We have attempted to present a number of p o s s i b i l -  i t i e s w i t h a minimum of p e r s o n a l b i a s , i n order t o p r o v i d e a broad b a s i s f o r a more d e t a i l e d  d i s c u s s i o n of one  or  two  s p e c i f i c mechanisms which we c o n s i d e r as most l i k e l y .  No  c l a i m i s made t h a t a l l p o s s i b i l i t i e s have been c o n s i d e r e d o t h e r s can almost  c e r t a i n l y be proposed, p a r t i c u l a r l y i f  complex combinations  of d i f f e r e n t mechanisms are c o n s i d e r e d .  However, i n view of the sharp and c l e a r l y d e f i n e d nature  of  19.  the s i g n a l we f e e l t h a t a r e l a t i v e l y simple e x p l a n a t i o n i s more l i k e l y - p r e f e r a b l y one which t i e s i n w i t h "prompt" d e t o n a t i o n e f f e c t s r a t h e r than w i t h delayed f i s s i o n - p r o d u c t decay. The l i s t i n g of mechanisms has been d i v i d e d two groups;  I: direct  into  "overhead" e f f e c t s ; I I : secondary  f o c u s mechanisms.  I.  l)  Hydromagnetic  The f i s s i o n  DIRECT EFFECTS  waves, a t o r near d e t o n a t i o n a l t i t u d e :  "bubble" expands a t a r a t e of about 100-1000  km/sec ( L a t t e r and L e L e v i e r , 1 9 6 3 ) . magnetic  and t h e r e f o r e a c t s as a p i s t o n on the e a r t h ' s mag-  netic f i e l d , modes.  I t i shighly dia-  s e t t i n g up hydromagnetic  waves i n the d i f f e r e n t  Some of these can almost c e r t a i n l y be i d e n t i f i e d  among the l a t e r a r r i v a l s , but i n as f a r as "phase B" I s concerned they do not f i t  the requirement of g l o b a l  synchron-  ism, s i n c e the r e l e v a n t p r o p a g a t i o n v e l o c i t i e s are of the order of a few hundred  t o a few thousand km/sec - f a r too low  to account f o r the simultaneous a r r i v a l s a t d i s t a n t Caner and Whitham (1962) proposed  locations.  hydromagnetic  shock wave i n the ionosphere as one p o s s i b l e e x p l a n a t i o n .  20.  T h i s was based on r e c o r d s from one s t a t i o n  ( V i c t o r i a ) only,  and on the assumption t h a t the 2 second d e l a y represented a p r o p a g a t i o n time. two  As soon as i t became e v i d e n t t h a t the  second I n t e r v a l r e p r e s e n t e d a " f i x e d d e l a y " t h i s mechanism  had t o be r u l e d o u t .  2)  Hydromagnetic waves i n h i g h - a l t i t u d e d u c t s :  proposed by Bomke e t a l i a  T h i s was  ( i 9 6 0 ) f o r the Argus I I I r e s u l t s  and assumes t h a t the energy i s propagated  w i t h i n "ducts" at  the a l t i t u d e s of maximum A l f v e n v e l o c i t y ,  i . e . 2000-3000 km.  The  d e l a y time f o r the energy t o reach these ducts was  assumed n e g l i g i b l e ,  and the a c t u a l nature o f the i n j e c t i o n  mechanism i s n o t c l e a r - hydromagnetic wave p r o p a g a t i o n t o the ducts, o r expansion  of the diamagnetic  r e q u i r e d d e l a y s of the order o f seconds.  buble,, would both The o n l y p o s s i b l e  i n j e c t i o n mechanism which would not i n t r o d u c e d e l a y i s the prompt x-ray o r r - r a y p u l s e .  significant  However, i n the  absence o f any s h a r p l y d e f i n e d "duct" boundary i t i s d i f f i c u l t t o see how s i g n i f i c a n t energy c o u l d be converted  into  hydromagnetic waves along the d u c t s . Quite apart from the time-delay o j e c t i o n , i t i s not c l e a r why s i g n i f i c a n t amounts of hydromagnetic energy should be r e f r a c t e d i n t o such d u c t s . trapped  Some energy c o u l d be  (even though i n e f f i c i e n t l y ) i n such a h i g h - v e l o c i t y  21.  l a y e r , but most of the energy would be conducted  i n the  lower-  v e l o c i t y ducts ( p a r t i c u l a r l y s i n c e the d e t o n a t i o n o c c u r r e d almost i n s i d e such a l o w - v e l o c i t y d u c t ) .  We would t h e r e f o r e  expect an almost continuous e f f e c t , w i t h amplitudes ing to  as the slower s i g n a l s a r r i v e .  increas-  T h i s does i n f a c t  the Argus I I I t e s t , where l a t e r a r r i v a l s ,  apply  although some-  times d i s t i n c t l y separate, were recorded w i t h l a r g e r amplitudes  (Berthold et a l i a ,  i960; Troitskaya, i 9 6 0 ) .  However,  i t does not f i t the S t a r f i s h d a t a . The main argument a g a i n s t t h i s mechanism as f a r as the S t a r f i s h data i s concerned  i s of course the g l o b a l  chronism and 2 second d e l a y .  Propagation v e l o c i t i e s at  these a l t i t u d e s are f i n i t e ,  syn-  even though very h i g h , and pro-  p a g a t i o n d e l a y s over the d i s t a n c e s i n v o l v e d would vary between 2 and 6  3)  seconds.  I o n i z a t i o n e f f e c t s due t o neutron-decay  betas:  The prompt neutron e m i s s i o n can account f o r some e f f e c t s d i r e c t l y , but these must be l i m i t e d to the g e o m e t r i c a l l y a c c e s s i b l e r e g i o n s , s i n c e neutron paths are not bent or deflected.  However, beta p a r t i c l e s which have decayed  from  these neutrons can be guided down t o i o n o s p h e r i c a l t i t u d e s by magnetic  f i e l d lines,  and t h e r e f o r e produce  ionization  e f f e c t s i n r e g i o n s not d i r e c t l y a c c e s s i b l e t o the  neutrons  22.  themselves.  F o r a f i s s i o n e x p l o s i o n , the  betas have t e r m i n a l e n e r g i e s of O.78 maximum c e n t e r e d at about 0.25  Mev  Mev,  neutron-decay with a very broad  (Zmuda e t a l i a ,  1963b).  T h i s mechanism was f i r s t proposed by C r a i n Tamarkin  and  (1961) to e x p l a i n sudden changes i n i o n i z a t i o n  f o l l o w i n g the Aug.  1958  tests.  oped r e c e n t l y by S e c h r i s t  I t has been f u r t h e r d e v e l -  (1962)., Zmuda e t a l i a  (1963a,b),  W i l l a r d and Kenney (1963), Kenney and W i l l a r d (1963), and others.  There  seems very l i t t l e  doubt t h a t t h i s mechanism  accounts f o r at l e a s t some of the observed prompt VLF  effects.  The known e x i s t e n c e of such a mechanism (as c o n t r a s t e d with the mainly h y p o t h e t i c a l nature of some of the o t h e r prop o s a l s ) makes i t very tempting t o a p p l y i t t o the geomagn e t i c data as w e l l , but t h e r e are two major o b j e c t i o n s : a)  The f i x e d time d e l a y .  Over the d i s t a n c e s i n v o l v e d the  onset times at d i f f e r e n t l o c a t i o n s should v a r y between m i l l i seconds and f r a c t i o n s of a second neutron energy of 1 Mev, 1.4  x 109  cm/sec).  (on the assumption  of mean  i . e . e j e c t i o n v e l o c i t i e s of  However, should the o r i g i n  spectrum  c o n t a i n an unexpectedly l a r g e f l u x of very low energy  neut-  rons, the d e l a y times c o u l d indeed reach 2 seconds at some remote l o c a t i o n s , but i n t h a t case t h e r e i s no g l o b a l synchronism.  F o r the p r e d i c t e d f i s s i o n spectrum,  the onset  time would be p r a c t i c a l l y i n s t a n t a n e o u s ( w i t h i n the time r e s o l u t i o n used i n t h i s r e p o r t , i . e . ±0.1  to 0.2  seconds).  23.  T h i s mechanism c o u l d t h e r e f o r e account f o r some o f the "phase A" a r r i v a l s , but not f o r "phase B". t e s t i n 1958? B e n i o f f  F o r the "Orange"  (quoted by Hodder, i960) r e p o r t e d s m a l l  ( f r a c t i o n a l gamma) s i g n a l s instantaneous w i t h the d e t o n a t i o n ( i ? ) a t two l o c a t i o n s remote from the d e t o n a t i o n p o i n t  (> 7000 km), but on f i e l d l i n e s a c c e s s i b l e t o neutron-decay betas.  Field  (1962) a t t r i b u t e d these s i g n a l s t o neutron  decay b e t a s . b)  The second major o b j e c t i o n i s amplitude.  F o r a 1.4  Megaton f i s s i o n bomb, the number o f i o n p a i r s formed by d e p o s i t i o n of betas a t the r e l e v a n t a l t i t u d e s about 75 p e r cm3 i n one second.  (80-100 km) i s  A rough estimate o f the  amplitude o f the r e s u l t i n g geomagnetic e f f e c t s can be obt a i n e d by comparison  1963).  I>  s i g n a l would be o f the order o f 0.1 t o 0.5  I f the prompt d e p o s i t i o n (at the f i r s t pass) alone  i s c o n s i d e r e d , the amplitudes would be even lower. Kenney and W i l l a r d s 1  formed  (Field,  F o r m i d - l a t i t u d e s t a t i o n s , H ~20-507, N0~lo4/cm3,  the r e s u l t a n t gamma.  with the d i u r n a l f l u c t u a t i o n s  Using  (1963) f i g u r e s , the number o f i o n p a i r s  i n a 1 cm^ f l u x tube over V i c t o r i a would account f o r  an i n c r e a s e o f o n l y about 7 i o n p a i r s p e r cm3.in the r e l e vant r e g i o n , i . e . a 0.01 t o 0.05 gamma s i g n a l .  Recent  e s t i m a t e s (Kenney, p r i v a t e communication) i n d i c a t e a p o s s i b l e i n c r e a s e i n these v a l u e s by a f a c t o r o f 10.  However, they  would s t i l l be too low (by a f a c t o r o f about 100) t o account f o r the observed  3O7 s i g n a l s .  24.  4)  F i s s i o n - p r o d u c t decay betas:  The decay of f i s s i o n  d u c t s p r o v i d e s a f a r more copious source of betas than  prothe  decay of the prompt neutrons.  The b u l k of t h e i r energy i s  d e p o s i t e d at a l t i t u d e s of 80 km  and below (mean energy about  1 Mev).  However, d e p o s i t i o n i s spread over a p e r i o d of  seconds f o l l o w i n g the d e t o n a t i o n .  A l s o these e l e c t r o n s  cannot be r a p i d l y t r a n s p o r t e d a c r o s s the f i e l d  lines  t h e i r prompt e f f e c t s must be c o n f i n e d to the f i e l d d i r e c t l y a c c e s s i b l e to f i s s i o n p r o d u c t s . expanding diamagnetic  The  bubble c o n f i n i n g the f i s s i o n  the d e t o n a t i o n p o i n t .  a l t i t u d e s the magnetic f i e l d p i n g expansion estimated.  lines  upwards-  p r o v i d e s a means f o r spreading these beyond the f i e l d , l i n e through  and  products  immediate  Since at these  i s the dominant f a c t o r f o r stop-  of the bubble,  i t s t e r m i n a l dimensions can be  L a t t e r and L e L e v i e r  (1963)  have shown t h a t the  t e r m i n a l c r o s s s e c t i o n area A of the f l u x - t u b e c o n t a i n i n g the bubble i s A  (  k  r  a  2)  =  3  where Z - a l t i t u d e i n km,  x  1 G  4  (1  +  ~T  )  Y  4  2  /  3  Rg - e a r t h r a d i u s i n km,  explosion y i e l d i n Kilotons.  The  and Y -  corresponding d e p o s i t i o n  area A ( k m ) at a l t i t u d e 80 km i s 2  0  F o r the " S t a r f i s h " t e s t A = 480  x 1 0 ^ km  2  (Radius 1 1 3 0 km).  (Z = 4 0 0 km,  (Radius = 1 2 4 0 km)  Y = 1 4 0 0 Kilotons), and A  Q  = 4 0 0 x 10^  km  These are maximum v a l u e s , based on the  2  25.  assumption t h a t the e n t i r e energy output goes i n t o expandingthe bubble. to 0.7  0.5  A more reasonable p r o p o r t i o n would be about  of t o t a l  yield.  Even though a small p r o p o r t i o n of the decay e l e c trons  (about 5$ - Colgate,. 1963)  i s ultimately injected into  h i g h e r L - s h e l l s through magnetic i n s t a b i l i t i e s , the bulk the d e p o s i t i o n i s l i m i t e d t o the area Ao. e f f e c t s due about 20° and 15°N  The  of  prompt ground  to i o n i z a t i o n are t h e r e f o r e l i m i t e d to a range of  at each conjugate area  ( i . e . about 15°S  to 35°S  to 35°N), and the mechanism i s inadequate to e x p l a i n  the geographic extent  of the  "phase B"  signals - quite  from other o b j e c t i o n s  (timing, sudden o n s e t ) .  apart  Transverse  d r i f t would of course extend the l o n g i t u d i n a l coverage,  but  even f o r very h i g h energy e l e c t r o n s the d r i f t r a t e i s f a r too  slow to account f o r "phase B"  arrivals.  5)  S e t t i n g up of l o c a l c o n d i t i o n s :  One  p o s s i b l e mechanism  suggested by S e l z e r ( p r i v a t e communication) i s t h a t the second d e l a y r e p r e s e n t s  a " s e t t i n g - u p " time of c o n d i t i o n s at  the p o i n t of o b s e r v a t i o n delay.  2  r a t h e r than a propagation  or  origin  In other words, the a c t u a l t r i g g e r i n g impulse  reaches a l l over the globe simultaneously able time r e s o l u t i o n ) and  "..the two  ( w i t h i n the  avail-  second d e l a y would have  been the time n e c e s s a r y f o r the process,  i n v o l v e d i n each of  26.  these l o c a l e x c i t a t i o n , to be performed" (Roquet, and S e l z e r , 1963).  Schlich  The t r i g g e r i n g mechanism i s not  speci-  f i e d , but e i t h e r the "phase A " p u l s e o r neutron-decay betas c o u l d f i t the t i m i n g requirements.  However, i t would  appear  to be almost i m p o s s i b l e to r e c o n c i l e the sharp sudden commencement w i t h t h i s h y p o t h e s i s .  U n l e s s some s o r t of break-  down e f f e c t can be formulated, any such p r o c e s s would gradual from the i n s t a n t of impulse a r r i v a l , s h a r p l y d e f i n e d at  II.  We  are now  ing  a b e t t e r name. on an i n t e r f a c e  r a t h e r than  H+2.  SECONDARY FOCUS MECHANISMS  c o n s i d e r i n g a group of p o s s i b l e mech-  anisms which we have c a l l e d of  be  "secondary f o c u s " type f o r want  These imply energy i n some form imping(or o t h e r c r i t i c a l r e g i o n ) and  setting  up a secondary f o c u s o f d i s t u r b a n c e from which energy i s r e emitted at (or c l o s e t o ) the speed of l i g h t .  The  two-  second d e l a y would be accounted f o r by p r o p a g a t i o n d e l a y between primary source and secondary f o c u s , or by the time r e q u i r e d t o s e t up the n e c e s s a r y c o n d i t i o n s f o r e m i s s i o n at the  secondary f o c u s , o r a combination of both.  We f e e l  that  In view of the c l o s e synchronism of the s i g n a l s recorded at w i d e l y separated l o c a t i o n s ,  such a "secondary f o c u s " mechanism  27.  i s f a r more l i k e l y than a d i r e c t primary "overhead" at each  effect  station. The a c t u a l nature of the energy c o n v e r s i o n and of  the s p e e d - o f - l i g h t t r a n s m i s s i o n mode are as y e t u n s p e c i f i e d the r e q u i r e d t h e o r e t i c a l work i s beyond the scope of t h i s preliminary investigation.  I t should be p o i n t e d out t h a t  the term "e.m. wave r a d i a t e d from a secondary f o c u s " must be used o n l y with r e s e r v a t i o n s , p a r t i c u l a r l y I f the d i s t u r b a n c e i s t o be propagated i n the earth-Ionosphere wave guide.  At  (0.25-0.30 cps) the f r e e - s p a c e wave-  the f r e q u e n c i e s i n v o l v e d  l e n g t h s are over 10^ km, i . e . o r d e r s of magnitude g r e a t e r than the dimensions distances.  of the wave guide o r the p r o p a g a t i o n  The s t a t i c  ( l / d 3 ) and i n d u c t i o n (1/d ) e f f e c t s 2  both become comparable t o r a d i a t i o n e f f e c t s a t d i s t a n c e s l e s s than 1/6 of a wavelength. On the o t h e r hand we c o u l d c o n s i d e r the s i g n a l as a s e r i e s of impulses, w i t h recovery I n between.  The observed  sine-shaped f l u c t u a t i o n s would then be e x p l a i n e d by f i l t e r i n g through the t r a n s m i s s i o n medium and/or i n s t r u m e n t a t i o n . T h i s would I n f a c t f i t some o f the proposed mechanisms b e t t e r than a monochromatic source emission, but i t s t i l l  l e a v e s un-  s p e c i f i e d the mode i n which these impulses are propagated at the speed of l i g h t .  28.  1)  Neutron-decay betas.  (and  r e j e c t e d ) the  We  direct  have p r e v i o u s l y  considered  overhead i o n i z a t i o n  effects  of  neutron-decay betas at each  station.  However, b e c a u s e  of  the  field-line  geometry,  pro-  focussing effect  of the  p o r t i o n o f them w i l l  be  in  (Kenney and  the  a u r o r a l zones  could provide  The  - the  I n s t a n t a n e o u s at the  time-scales  s e c o n d s t o a b o u t 0.2  seconds,  sidered  amplitudes.  r e s p o n s i b l e f o r the ported the  conjugate  areas  Willard,  1963).  This  main o b j e c t i o n s t o t h i s  2 second time d e l a y  the  In the  a p o s s i b l e t r i g g e r i n g mechanism f o r  disturbances. a)  deposited  a high  considered,  and  b)  the  are:  practically  I.e.  milli-  previously  T h i s mechanism i s a l m o s t (instantaneous?)  secondary  theory  deposition Is  and  con-  certainly  auroral displays re-  f r o m a u r o r a l zone l o c a t i o n s ^ and  probably  also f o r  a b n o r m a l l y h i g h - a m p l i t u d e h o r i z o n t a l component d e f l e c -  tion  reported  f r o m an  a u r o r a l zone m a g n e t i c  (Meanook; Cook, p r i v a t e c o m m u n i c a t i o n ) . unlikely  t o be  It neutron  delay  be  pointed  (i.e. fission  have t o be  large flux  longer o f an  should  spectrum  mechanism may very  r e s p o n s i b l e f o r the  (2  of very  out  that  i f our  explosion)  signal.  assumed  i s Incorrect,  this  In p a r t i c u l a r ,  if a  energy neutrons i s produced,  s e c o n d s ) c o u l d be  a u r o r a l zone  I t I s however  g l o b a l "phase B"  reconsidered. low  observatory  accounted f o r i n the  secondary focus,  t h e o r e t i c a l l y p o s s i b l e as f a r as the  and  case  t h e mechanism may  timing  a  i s concerned.  be  29.  However, the a v a i l a b l e amplitude data p o i n t towards a source i n the d e t o n a t i o n area r a t h e r than In the a u r o r a l r e g i o n s  (Bomke e t a l i a , 1963).  2)  F i s s i o n - p r o d u c t decay b e t a s .  We have p r e v i o u s l y d i s -  cussed the e f f e c t s of f i s s i o n - p r o d u c t decay betas, and  con-  c l u d e d t h a t they do not f i t "phase B" o b s e r v a t i o n s i n as f a r as d i r e c t overhead i o n i z a t i o n e f f e c t s are concerned.  How-  ever, the r e l a t i v e l y c o n c e n t r a t e d d e p o s i t i o n of these betas i n the conjugate area c o u l d p r o v i d e a p o s s i b l e f o c u s mechanism. field  secondary-  The t r a n s i t time of t h e betas along the  l i n e s i s p r a c t i c a l l y i n s t a n t a n e o u s at t h e time  resol-  u t i o n s c o n s i d e r e d , which r a i s e s t h e q u e s t i o n of t h e 2 second delay.  The expansion time of the bubble i s of the r i g h t  order of magnitude.  Colgate (1963) e s t i m a t e d 2.5  seconds  as the time r e q u i r e d f o r the bubble to reach i t s t e r m i n a l dimensions R = 1000 to  km.  .A p r e c i s e f i g u r e would be  difficult  o b t a i n i n view of the u n c e r t a i n t i e s i n parameters - i n  p a r t i c u l a r , the p r o p o r t i o n of the t o t a l y i e l d which i s a v a i l able f o r expansion of the bubble c o u l d vary between 30$  and  70$. A continuous p r o c e s s r a t h e r than a sudden r e l e a s e c o u l d be expected,  s i n c e e n e r g e t i c e l e c t r o n s would be  u o u s l y e s c a p i n g from the bubble d u r i n g expansion.  contin-  However,  30.  t h e e x p a n s i o n o f t h e b u b b l e may a c t u a l l y p r o v i d e some of energy would  " f i l t e r i n g " mechanism - h i g h e r e n e r g y  lose  energy  of the magnetic stopped  i n expanding  field,  until  the bubble  to spiral  against  at the time t h e expansion i s flux i s  T h i s mechanism d o e s n o t e x p l a i n t h e  o s c i l l a t o r y nature of the s i g n a l t r o n s have much s h o r t e r p e r i o d s ) ,  (since  the m i r r o r i n g  elec-  but i t appears t o f i t the  requirements f o r the i n i t i a l  The  the pressure  t o t h e c o n j u g a t e a r e a s and t o t r i g g e r t h e  secondary disturbance.  timing  electrons  (H+1.9 s e c ? ) a r e a s o n a b l y m o n o e n e r g e t i c  released  sort  i m p u l s e o f "phase  spectral characteristics  of f i s s i o n  d e c a y b e t a s have b e e n d i s c u s s e d b y Zmuda e t a l i a  B".  decay (1963a), b u t  t h e g e n e r a l a r g u m e n t s f o r t h i s p a r t i c u l a r mechanism a r e p r a c t i c a l l y u n a f f e c t e d by the p r e c i s e since the beta t r a n s i t  A  i  distribution,  time t o t h e c o n j u g a t e a r e a i s s h o r t  compared w i t h 2 s e c o n d s ,  3)  spectral  even f o r low energy  electrons.  Hydromagnetic E l e c t r o m a g n e t i c c o n v e r s i o n a t the lower Ionosphere boundary. v e r y s i m p l e , and t h e r e f o r e  attractive,  t i v e l y p r o p o s e d b y Bomke e t a l i a wave p r o p a g a t e s v e r t i c a l l y point,  (1963).  m o d e l was t e n t a A  hydromagnetic  downward f r o m t h e d e t o n a t i o n  and o n r e a c h i n g t h e l o w e r i o n o s p h e r e b o u n d a r y  a secondary d i s t u r b a n c e which speed o f l i g h t .  s e t s up  i s then propagated at the  The c o n v e r s i o n e f f i c i e n c y b e t w e e n  hydro-  31.  magnetic (h.m.) and e l e c t r o m a g n e t i c interface  (e.m.) waves at a sharp  (which i s s a t i s f i e d at the wavelengths i n v o l v e d )  i s of the order of one t o a few p e r c e n t . o b t a i n e d a f i g u r e of 1$, was  Kahalas  (i960)  but p o i n t e d out t h a t h i s d e r i v a t i o n  based on assumptions which are not n e c e s s a r i l y v a l i d f o r  the lower  ionosphere. The p r o p a g a t i o n time f o r a hydromagnetic wave  between the d e t o n a t i o n p o i n t and 80 km b l y account f o r the 2 second d e l a y .  altitude could possiA precise  of t h i s p r o p a g a t i o n d e l a y would be meaningless,  computation s i n c e the  p r o p e r t i e s of the medium below the d e t a o n a t i o n p o i n t would have been d r a s t i c a l l y a l t e r e d by the prompt (x-rays i n p a r t i c u l a r ) .  radiation  An estimate of l i m i t i n g  has been worked out i n Appendix I I .  values  A 2-second d e l a y  appears t o be at the extreme l i m i t of the a c c e p t a b l e range f o r r a d i a t i n g temperatures  up to 2 kev,  but would be w e l l  w i t h i n the acceptable range f o r higher-temperature  devices  ( f u s i o n bomb?). There are two  o b j e c t i o n s to t h i s model:  monochromatic nature of the observed  Although  The  s i g n a l does not f i t  the e s s e n t i a l l y i m p u l s i v e ( i . e . broadband) o r i g i n bance.  a)  distur-  s e l e c t i v e p r o p a g a t i o n c o u l d e x p l a i n the  predominance of c e r t a i n fequency bands (Jacobs and Watanabe,  1962), i t i s u n l i k e l y t h a t t h i s c o u l d be e f f e c t i v e enough over the short p a t h l e n g t h i n v o l v e d to account f o r a sharp  frequency s e l e c t i o n as observed. b) The  main o b j e c t i o n a g a i n s t t h i s mechanism i s the  t h a t lower a l t i t u d e t e s t s ( i n p a r t i c u l a r below 80 km)  "Teak", at or  do not produce s i m i l a r e f f e c t s .  the c o n v e r s i o n  of e x p l o s i o n k i n e t i c energy i n t o hydromagat the  altitudes.  c l o s e the  altitude,  just  Admittedly  n e t i c forms i s c o n s i d e r a b l y more e f f i c i e n t Nevertheless,  detonation  fact  was  c o n s i d e r i n g how  higher "Teak"  to t h i s h y p o t h e t i c a l "secondary f o c u s "  some comparable e f f e c t s (even I f w i t h much lower  amplitudes) should have been observed, w i t h a reduced or zero d e l a y .  I t should be mentioned t h a t t h i s argument i s  somewhat complicated experiments may  by the p o s s i b i l i t y t h a t s h i e l d i n g  have been i n c l u d e d i n some of the  F o r example, r e l a t i v e l y simple  tests.  d e v i c e s can reduce the prompt 1  1 r a d i a t i o n f l u x by f a c t o r s of 100  or more, and  energy l e v e l s by f a c t o r s of 10-20  ( L a t t e r , Herbst  Watson, I 9 6 I ; L a t t e r and L e L e v i e r , type and  1963).  and  A l s o the a c t u a l  c o n s t r u c t i o n of the bomb, i n p a r t i c u l a r the  m a t e r i a l , has  a s t r o n g i n f l u e n c e on the  t e d prompt r a d i a t i o n .  u n l i k e l y t h a t major ones such as complications. not o n l y do we  casing  spectrum of the  Although s h i e l d i n g experiments  have been i n c l u d e d i n some of the  Nevertheless,  smaller tests,  emitmay very  such  I t should be kept i n mind t h a t  have a minute sample, but we  arguments as to why  i t Is  "Teak" i n c l u d e d any  r e l i a b l e o r i g i n i n f o r m a t i o n on these l y any  the mean  few  do not even have  tests.  Consequent-  o n l y c e r t a i n t e s t s do or do  produce c e r t a i n r e s u l t s must be used with  caution.  not  33.  4) In the  Hydromagnetic  Impulse guided along the f i e l d - l i n e .  t h i s mechanism a hydromagnetic Impulse i s guided a l o n g f i e l d - l i n e through the d e t o n a t i o n p o i n t , w i t h p a r t i a l  r e f l e c t i o n s a t each end.  The mechanism i s e f f e c t i v e l y a  v a r i a n t o f the p r e v i o u s one, but might a l s o e x p l a i n the o s c i l l a t o r y nature of the s i g n a l , the observed p e r i o d , and the  absence of s i m i l a r e f f e c t s from l o w e r - a l t i t u d e  I t would a l s o f i t the damped amplitude e f f e c t ,  tests.  and the  "bounce" p e r i o d i s of the r i g h t o r d e r (3-4 seconds). A simple c o n s i d e r a t i o n of the geometry  involved  i n d i c a t e s a major t i m i n g v s . p e r i o d o b j e c t i o n .  Figure 6  shows the r e l e v a n t f i e l d - l i n e ,  drawn t o s c a l e .  It i s  obvious t h a t i f t (the i n i t i a l  delay, H-»P) i s 2 seconds,  T (the f i r s t seconds. the  bounce p e r i o d , P-*R) cannot be as low as 3.5-4  There i s , however, a p o s s i b l e e x p l a n a t i o n f o r  d i s c r e p a n c y - the " r e f l e c t i o n p o i n t " P i s i n the d i r e c t  r a d i a t i o n zone, and the medium around i t undergoes vast i n stantaneous changes i n i o n i z a t i o n due t o prompt  radiation,  i n p a r t i c u l a r x-rays (which f o r the spectrum of a f i s s i o n bomb d e p o s i t most o f t h e i r energy at a l t i t u d e s of 70 t o 90 km) - see Appendix I I . lower a l t i t u d e s  The r - r a y s d e p o s i t energy down t o  (about 20-30 km f o r the Mev energy range).  Although the i o n i z a t i o n due to the prompt 7-ray p u l s e decays w i t h i n microseconds, some p e r s i s t i n g n e t i o n i z a t i o n at these lower a l t i t u d e s  (over a few seconds) r e s u l t s from delayed  SCALE  FIG. 6  1000 KM  FIELD  LINE  "STARFISH"  THROUGH  THE  TEST  JULY  OF  DETONATION 9,1962.  POINT  35.  fission-product r-rays. the f i r s t  pass  I t Is therefore p o s s i b l e that f o r  (H-*P) the medium was p r a c t i c a l l y opaque t o  h.m. waves, o r t h a t the necessary  (interface  c o n d i t i o n s a t p o i n t P d i d not e x i s t .  sharpness?)  The i n i t i a l  "secondary  f o c u s " would t h e r e f o r e be s e t up at p o i n t R i n the southern hemisphere. for  T h i s removes the timing-geometry  t (H-»R) = 2 seconds,  reasonable. altitudes  objection:  T (R-+P) = 3-4 seconds i s q u i t e  C r a i n (1963) has shown t h a t at the r e l e v a n t  (75 km) the x-ray induced i o n i z a t i o n decays with  t i m e - c o n s t a n t s o f the order of a few seconds.  Consequently,  when the r e f l e c t e d wave reaches P ( i . e . a f t e r 5-6  seconds,  H-»R-*P) the " i n t e r f a c e " may have s u f f i c i e n t l y recovered t o permit e f f i c i e n t energy c o n v e r s i o n (h.m. -* e.m.) and r e flection.  The very s l i g h t r e v e r s e movement which  preceded  the main movement on s e v e r a l r e c o r d i n g s (e.g. V i c t o r i a , F i g u r e 1, 1963) pass.  o r Jicamarca - see F i g u r e 5 of Casaverde e t a l i a ,  may r e p r e s e n t the e f f e c t of the "aborted" f i r s t The f a c t t h a t the d e l a y H-*P was o n l y s l i g h t l y  H-* P less  than H - R would be reasonable, i n view o f the l a r g e x-ray induced i n i t i a l  i n c r e a s e i n i o n i z a t i o n over the H-» P sec-  t i o n - see Appendix I I . There i s an i n t e r e s t i n g ambiguity  i n t h i s model.  Does energy e m i s s i o n occur at both m i r r o r p o i n t s ( i . e . are there 2 secondary  s o u r c e s ) , o r does o n l y the southern f o c u s  e x i s t , with the n o r t h e r n end having recovered  sufficiently  36.  to permit passage of the hm wave and r e f l e c t i o n , but not f o r e f f i c i e n t h.m.  e.m.  energy conversion?  t i m i n g data are concerned, 3.5-4  does the observed time f o r a one way end,  In as f a r as  t h i s q u e s t i o n can be r e s t a t e d as:  second p e r i o d r e p r e s e n t the  transit  bounce (R-* P or P-* R), i . e . f o c u s at each  or does i t represent a f u l l m i r r o r p e r i o d ( R - * P — R ) ,  f o c u s at southern end only?  I.e.  Even under normal c o n d i t i o n s  the A l f v e n v e l o c i t i e s are not known to b e t t e r than a f a c t o r of 1.5-2,  and w i t h the a r t i f i c i a l  ionization  changes over  p a r t s of the path i t becomes i m p o s s i b l e to compute the m i r r o r p e r i o d with s u f f i c i e n t accuracy to r e s o l v e the above ambiguity.  The  l i m i t i n g cases f i t j u s t about e q u a l l y the  possibilities.  F o r u n d i s t u r b e d n i g h t - t i m e c o n d i t i o n s , the  mean A l f v e n v e l o c i t i e s at a l t i t u d e s  800,  two  of 350,  500* 750 km are  1000 and 2000 km/sec r e s p e c t i v e l y (Jacobs and Watanabe,  1962), and a f u l l m i r r o r p e r i o d of 4 seconds i s p o s s i b l e . Under d i s t u r b e d c o n d i t i o n s these v e l o c i t i e s are reduced  by  a f a c t o r of 2 or more, and the 4-second p e r i o d would have to be the time per one-way t r a n s i t , The  i . e . f o c u s at each  ambiguity might be r e s o l v a b l e on t h e o r e t i c a l  end.  grounds  once the exact c o n d i t i o n s f o r r e f l e c t i o n and energy convers i o n are e s t a b l i s h e d .  In any case, the o v e r a l l  t h i s model i s i n no way  a f f e c t e d by t h i s  We tative  v a l i d i t y of  ambiguity.  are w e l l aware of the weaknesses i n t h i s  treatment,  and c o n s i d e r a b l e t h e o r e t i c a l  quali-  work on the  37.  c o n d i t i o n s f o r h.m. -* e.m.  energy  out b e f o r e such a model I s f u l l y ever, is  c o n v e r s i o n must be c a r r i e d acceptable.  I t does,  how-  f i t the experimental timing data extremely w e l l -i t  t h e o n l y t h e o r y so f a r w h i c h f i t s  ditions,  i n c l u d i n g the decrease  e x p l a i n e d by the f a c t  that  a l l the s p e c i f i e d  i n period.  on t h e f i r s t  con-  T h i s c o u l d be  pass the i o n d e n s i t y  o v e r p a r t s o f t h e p a t h would have been s i g n i f i c a n t l y i n c r e a s e d b y d e t o n a t i o n p r o d u c t s t r a v e l l i n g f a s t e r t h a n t h e h.m. wave, and t h e A l f v e n v e l o c i t y the  square  normal. of  (which i s I n v e r s e l y p r o p o r t i o n a l t o  r o o t o f t h e I o n d e n s i t y ) w o u l d be l o w e r As t h e a r t i f i c i a l  the o r d e r o f seconds)  i o n i z a t i o n decays  the A l f v e n v e l o c i t y  t h e bounce p e r i o d d e c r e a s e s . i n bounce p e r i o d o v e r about effective  initial  unreasonable  The o b s e r v e d 15  seconds  than  (time c o n s t a n t s I n c r e a s e s and  20$-30$  decrease  w o u l d i n d i c a t e an  increase In i o n density of  50$-70$  - not  f o r t h i s p a r t i c u l a r path which i s p a r t l y  , prompt r a d i a t i o n zone and a l s o  i n the  along the guided path of f a s t  betas.  There  (though  v e r y weak) c o n -  f i r m a t i o n f o r a " s o u r c e " o f 3-second p e r i o d  oscillations i n  the  southern hemisphere.  amplitude Zealand that  i s some i n d e p e n d e n t  comparisons  Poletti  of t e l l u r i c  stations with I d e n t i c a l  and Gadsden  (1962),  from  r e c o r d i n g s a t two New  instrumentation, conclude  t h e s o u r c e o f 3 - s e c o n d p e r i o d p u l s a t i o n s must have b e e n  "a few h u n d r e d  k i l o m e t e r s , a t most, t o t h e n o r t h o f L a u d e r  38.  (50° geomag. l a t . ) " ,  i . e . a t about 40°S geomag. ,  This i s  of course much f u r t h e r south than p o i n t R (by about 20°, i.e.  2000 km).  A l s o the p u l s a t i o n s r e f e r r e d t o are not  those of "phase B" (which were u n f o r t u n a t e l y o f f - s c a l e at both s t a t i o n s ) , but some l a t e r a r r i v a l s .  Consequently no  great amphasis can be put on t h i s evidence  i n support of the  proposed  model.  Although i t may be r e l e v a n t , i t i s prob-  a b l y due t o some e n t i r e l y d i f f e r e n t c o n j u g a t e - p o i n t  5)  Hydromagnetic wave along the f i e l d - l i n e .  effect.  Some of the  p o i n t s d i s c u s s e d f o r the p r e v i o u s model can a l s o be a p p l i e d to  a l o n g - p e r i o d hydromagnetic wave p r o p a g a t i n g along the  field-line  through the d e t o n a t i o n p o i n t .  The 2--second  d e l a y would r e p r e s e n t the p r o p a g a t i o n time o f the wave f r o n t t o the conjugate p o i n t .  The d i s t i n c t i o n between t h i s  model and the p r e c e d i n g one should be c l e a r l y  understood.  In the p r e c e d i n g model we c o n s i d e r e d a hydromagnetic ( i . e . broadband "wave-packet") which i s propagated field-line. the impact quency.  In  along the  0.25 p.p.s. r e p r e s e n t s the r e p e t i t i o n r a t e o f of t h i s impulse  on the i n t e r f a c e , not a wave f r e -  The h i g h e r component f r e q u e n c i e s of the pulse are  e i t h e r not converted i n t o e l e c t r o m a g n e t i c forms, filtered  impulse  o r are  out by p r o p a g a t i n g media and/or i n s t r u m e n t a t i o n .  t h i s model we c o n s i d e r a s i n g l e hydromagnetic standing  wave, frequency 0.25 cps, with d i r e c t c o u p l i n g t o a 0.25 cps  39.  electromagnetic The chromatic  wave at an i n t e r f a c e .  main o b j e c t i o n t o t h i s mechanism i s the mono-  nature  of the s i g n a l .  I t i s however p o s s i b l e t h a t  p r e f e r e n t i a l e x c i t a t i o n of the eigen p e r i o d s , combined  with  s e l e c t i v e h.m. t o e.m. c o n v e r s i o n o f c e r t a i n frequency  bands,  c o u l d provide  a suitable explanation.  a c t e r i s t i c p e r i o d can be estimated T = j" ( V " A ) • ds over the f i e l d - l i n e 2//  1958).  The fundamental char-  by numerical i n t e g r a t i o n (Obayashi and Jacobs,  I t l i e s between about 6 and 15 seconds ( u s i n g the  A l f v e n v e l o c i t i e s f o r n i g h t time d u r i n g p e r i o d s o f maximum and minimum sunspot a c t i v i t y r e s p e c t i v e l y ) .  I n view o f the  i n c r e a s e i n I o n i z a t i o n due t o r a d i a t i o n , and of the extreme d i s t o r t i o n of the f i e l d - l i n e by the diamagnetic bubble, a precise determination  of e i g e n - p e r i o d s  i s impossible.  The  observed p e r i o d s are t h e r e f o r e w e l l w i t h i n an acceptable range o f v a l u e s f o r the f i r s t  harmonic.  T h i s mechanism f i t s the o b s e r v a t i o n a l data i n a l l respects.  The decrease i n p e r i o d i s a l s o o b t a i n e d  - as the  a r t i f i c i a l l y - i n d u c e d i n c r e a s e i n i o n i z a t i o n decays, the A l f v e n v e l o c i t y i n c r e a s e s and the e i g e n - p e r i o d  decreases.  There appears t o be no obvious way o f d i s t i n g u i s h i n g between t h i s and the p r e c e d i n g model on the b a s i s o f the o b s e r v a t i o n a l data, but we f e e l t h a t the standing-wave model i s p r e f e r a b l e , even i f o n l y on a e s t h e t i c grounds alone.  I t does not  i n v o l v e any e l a b o r a t e c o n s i d e r a t i o n s o f geometry or f o c u s  4o.  location,  and i t does not r e q u i r e complex f i l t e r i n g mechan-  isms t o e x p l a i n the observed q u a s i - s i n u s o i d a l  6)  Protons guided along the f i e l d - l i n e .  signals.  The major source  of prompt protons from a f i s s i o n p r o c e s s i s neutron  decay.  The protons have e s s e n t i a l l y the same k i n e t i c energy as the parent n e u t r o n s .  The energy d i s t r i b u t i o n of prompt neutrons  from a f i s s i o n p r o c e s s has been d i s c u s s e d i n d e t a i l by  Bonner, P e r r e l , Rinehart (1952), H i l l  (1952), and Watt  (1952).  I n the energy range 0.075 Mev t o 17 Mev i t can be r o u g h l y r e p r e s e n t e d by the s e m i - e m p i r i c a l formula g i v e n by Watt  (1952): N(E) = 4.75  x 10  6  No i n f o r m a t i o n i s a v a i l a b l e  s i n h ( 2 E ) 2 exp (-E) X /  f o r e n e r g i e s below 75 Kev.  F i g u r e J shows a p l o t o f the energy d i s t r i b u t i o n up t o 7 Mev. The  spectrum has a very broad maximum c e n t e r e d at 0.8 Mev -  e m i s s i o n i s p r a c t i c a l l y constant ( w i t h i n a few p e r c e n t ) between 0.4 Mev and 1.3  Mev.  Even though e n e r g i e s range t o  above 18 Mev, most of the neutrons are below 2 Mev, the f a l l o f f b e i n g p r a c t i c a l l y e x p o n e n t i a l above 2 Mev. For  t h i s p a r t i c u l a r f i e l d - l i n e the two-way m i r r o r  p e r i o d of 1 Mev p r o t o n s i s about  2 seconds  (Zmuda e t a l i a ,  1963a), 3 seconds f o r 0.4 Mev, and 4 seconds f o r 0.25 Mev, which i s o f the r i g h t o r d e r f o r the observed "phase B"  ~t  1  1  I  1  1  1  0  I  2  3  4  5  6  FIG. 7  ENERGY  SPECTRUM  OF FISSION  *•  Neutron Energy  NEUTRONS  (MEV)  42.  periods.  I n t h i s c o n n e c t i o n i t should be mentioned t h a t  Zmuda e t a l i a  (1963a) r e p o r t e d 10-second p e r i o d c y c l i c VLP  e f f e c t s over the NPG-APL/JHU path, which they  tentatively  a t t r i b u t e d t o 0 . 4 Mev protons m i r r o r i n g over NPG. of  I n view  the u n c e r t a i n t i e s i n f i e l d - l i n e geometry and other para-  meters, i t i s p o s s i b l e t h a t the two e f f e c t s c o u l d be reconc i l e d t o f i t the m i r r o r i n g o f protons with the same energy (say  C . 3 - 0 . 4 Mev) along d i f f e r e n t The  field-lines.  same o b j e c t i o n s of timing-geometry  (initial  d e l a y v s . p e r i o d ) which were d i s c u s s e d i n one of the preceding  mechanisms, can be. made t o t h i s mechanism and the same  s o l u t i o n can be proposed,  v i z . the f i r s t  r e f l e c t i o n and  energy c o n v e r s i o n occurs a t the southern end. the same ambiguity  Here again  as i n the p r e v i o u s model a r i s e s : does a  " f o c u s " e x i s t at each end, o r o n l y at the southern end. t h i s case, however, the ambiguity can be s o l v e d .  In  The  r e l e v a n t r e f l e c t i n g a l t i t u d e s are h i g h e r (about 100 km f o r 0 . 4 Mev p r o t o n s ) , and the x-ray induced i o n i z a t i o n decays far  more s l o w l y at these a l t i t u d e s than a t 80 km.  a l t i t u d e s 95 t o 115  For  km the decay constant v a r i e s between 4 0 0  and 3000 seconds ( C r a i n , 1963), depending on the exact tude and magnitude of the I o n i z i n g p u l s e . at  I f t h i s model i s  a l l v a l i d , there can be o n l y one "secondary  the southern end),  alti-  focus" (at  and the 3 . 5 - 4 seconds r e p r e s e n t a f u l l  m i r r o r p e r i o d , i . e . protons with e n e r g i e s 0.25 t o 0.20 Mev.  43.  T h i s p r o v i d e s the p o s s i b i l i t y of an experimental the v a l i d i t y of t h i s model.  Observed s i g n a l  should be h i g h e r near the conjugate d e t o n a t i o n point,. but the evidence Bomke e t a l i a Hawaii was  check on  amplitudes  p o i n t than near the  T h i s does not appear to be the  i s base! on o n l y one  case,  set of o b s e r v a t i o n s :  (1963) r e p o r t e d t h a t the amplitude  recorded at  h i g h e r than t h a t recorded at Samoa by a f a c t o r of  about f o u r . Another major o b j e c t i o n t o t h i s mechanism i s the sharpness  of the commencement, and the c l e a r l y d e f i n e d f r e -  quency of the subsequent swings.  In view of the  energy d i s t r i b u t i o n spectrum of the protons, (seconds  a  broad  continuous  r i s e time) commencement and complex waveforms c o u l d  be expected.  Also t h i s model p r o v i d e s no e x p l a n a t i o n f o r  the d e c r e a s i n g p e r i o d .  However, should the e m i s s i o n t u r n  out to c o n t a i n a major, reasonably monoenergetic source low-energy (0.2-0.4 Mev)  protons,  be r e c o n s i d e r e d i n more d e t a i l . that the presented emitted neutrons  the mechanism may  of  have to  I t should be p o i n t e d out  s p e c t r a l d i s t r i b u t i o n data r e f e r to  i n general.  The  spectrum of the  propor-  t i o n which escapes the d e b r i s area would probably be toward the low-energy end due  shifted  to s h i e l d i n g by the d e b r i s .  (The s h i f t c o u l d be c o n s i d e r a b l e i f d e l i b e r a t e neutron s h i e l d i n g had been p a r t of the t e s t , but t h i s i s u n l i k e l y i n view of the bulk of the necessary  shields.)  However, the  44.  general feature  ( i . e . broad maximum, almost 2 Mev "wide")  would presumably remain unchanged,  even though i t may be  centered around a lower energy, so t h a t t h i s does not f i t the requirement f o r a monoenergetic  flux.  CONCLUSION  The p r e c e d i n g d i s c u s s i o n i n d i c a t e s t h a t hydromagnetic s t a n d i n g waves a l o n g the f i e l d - l i n e through the d e t o n a t i o n p o i n t p r o v i d e the most l i k e l y e x p l a n a t i o n f o r the "phase B" s i g n a l .  I t i s the o n l y one of the mechanisms  d i s c u s s e d i n t h i s r e p o r t whieh f i t s a l l the o b s e r v a t i o n a l data, and i s not dependent  on a knowledge of the bomb type  ( f i s s i o n and/or f u s i o n ) . Whatever the t r i g g e r i n g mechanism, f u r t h e r theor e t i c a l work i s r e q u i r e d on the energy c o n v e r s i o n mechanism at the secondary focus, and on the s p e e d - o f - l i g h t propagat i o n of the secondary d i s t u r b a n c e . No unique s o l u t i o n i s c l a i m e d - o t h e r models are p o s s i b l e , and w i t h the l i m i t e d amount of data a s e n s i t i v e enough c r i t e r i o n f o r d i s t i n g u i s h i n g between the d i f f e r e n t mechanisms i s hard t o d e f i n e .  Some a d d i t i o n a l l i n e s of  approach t o t h i s problem are suggested i n Appendix I, which may y i e l d the n e c e s s a r y i n f o r m a t i o n i f a d d i t i o n a l observat i o n a l data become a v a i l a b l e .  45.  APPENDIX I ADDITIONAL LINES OP APPROACH  1)  More p r e c i s e t i m i n g c o n s i d e r a t i o n s .  There are  apparent  time d i s c r e p a n c i e s of the order of 0 . 1 - 0 . 2 seconds between some of the b a s i c s t a t i o n s . r e a l , being probably due ponents or other f a c t o r s .  These are almost  c e r t a i n l y not  to d i f f e r e n c e s i n the recorded comI f a network of h i g h l y accurate  ( b e t t e r than 50 m i l l i s e c o n d s ) , i d e n t i c a l l y  instrumented  o b s e r v a t i o n s become a v a i l a b l e , u s e f u l i n f o r m a t i o n c o u l d probably be e x t r a c t e d which would d i s t i n g u i s h between the d i f f e r e n t models.  U n f o r t u n a t e l y , because of the  relatively  slow r i s e time of n a t u r a l "sudden" geomagnetic phenomena, most r e s e a r c h e r s i n t h i s f i e l d have not developed  or a p p l i e d  the t i m i n g techniques and d i s c i p l i n e s which are r e q u i r e d f o r this  type of work.  Highly standardized instrumentation  and r e c o r d i n g of the same magnetic-coordinate a l s o necessary f o r h i g h - a c c u r a c y  component are  t i m i n g work, s i n c e the  exact commencement of the d i s t u r b a n c e i s otherwise hard to define. suitable  In view of the d i f f i c u l t y i n assembling  even a few  ( i O . l sec) o b s e r v a t i o n s on a g l o b a l s c a l e , i t i s  d o u b t f u l whether a set of such i o . 0 5 l e a s t i n the u n c l a s s i f i e d domain.  sec data e x i s t s ,  at  46.  2)  Amplitude c o n s i d e r a t i o n s .  The  present  r e p o r t has been  based almost e n t i r e l y on t i m i n g c o n s i d e r a t i o n s . of  An a n a l y s i s  a m p l i t u d e - l o c a t i o n r e l a t i o n s c o u l d go a l o n g way  the removal of the ambiguity  towards  between the d i f f e r e n t mechan-  isms, through the d e t e r m i n a t i o n s  of f o c u s l o c a t i o n ,  atten-  u a t i o n c h a r a c t e r i s t i c s , and p o s s i b l e a n i s o t r o p l e s i n propagation.  U n f o r t u n a t e l y the data p u b l i s h e d so f a r are u n s a t i s -  f a c t o r y from t h i s p o i n t of view, f o r two a)  reasons:  Most of the magnetic r e c o r d i n g s o b t a i n e d with the appro-  p r i a t e bassband went o f f - s c a l e d u r i n g the f i r s t fluctuations.  "phase B"  T h i s means that o n l y a lower amplitude  limit  can be assigned, depending on the f u l l - s c a l e range of the p a r t i c u l a r i n s t r u m e n t a t i o n - which v a r i e s between 0.5 50r  for different  limit of  stations.  and  Recorders f i t t e d with s c a l e -  ( b i a s ) s t e p p i n g mechanisms i n t r o d u c e d an u n c e r t a i n t y  1 or even 2 steps ( i . e . 1-2  full  s c a l e ranges) because of  the u n u s u a l l y r a p i d f u l l - s c a l e e x c u r s i o n s - see f o r example  Baker and Strome (1962). b)  V a r i a b i l i t y i n recorded component and i n i n s t r u m e n t a t i o n .  Quite apart from t e l l u r l c s amplitude  (which cannot be i n c l u d e d f o r  comparisons) there are 6 n o r m a l l y  acceptable ways  of  choosing  a single-component r e c o r d i n g (D, H, Z, X, Y, F ) ,  of  which f i v e are u s u a l l y recorded with e i t h e r  l i n e a r or rate-of-change  detectors.  amplitude-  T h i s means e l e v e n  d i f f e r e n t methods - q u i t e apart from the widely v a r y i n g f r e quency response c h a r a c t e r i s t i c s .  T h i s makes i t almost  47.  Impossible to e x t r a c t amplitude comparisons to b e t t e r than an order of magnitude, even i f the r e c o r d i n g s had remained on s c a l e .  A l s o , v e r t i c a l components,  p a r t i c u l a r l y at the  f r e q u e n c i e s i n v o l v e d i n the "phase B" s i g n a l , are f a r too h e a v i l y dependent on l o c a l g e o l o g i c c o n d i t i o n s to be u s e f u l f o r amplitude comparisons.  In view of the a v a i l a b i l i t y of  commercially-manufactured t o t a l f o r c e instruments, i t was to be hoped t h a t at l e a s t a number of t o t a l - f i e l d  ampli-  tudes would have been a v a i l a b l e from i d e n t i c a l equipment. However, i n some cases the l a r g e and r a p i d v a r i a t i o n s of the "phase B" s i g n a l were beyond the range which c o u l d be e f f e c t i v e l y recorded (because the c o u n t i n g p e r i o d becomes comparable with the time s c a l e of the f l u c t u a t i o n s ) ,  and  "phase B" r e c o r d i n g s on some t o t a l - f i e l d instruments must be used with c a u t i o n .  F o r example, U n t e r b e r g e r and B y e r l y  (I962) r e p o r t e d that two Rubidium Vapour magnetometers opera t i n g at the same l o c a t i o n (5 f e e t apart) gave coherent r e c o r d i n g s up t o H+2  sees and a f t e r H+30 sees, but not d u r i n g  the "phase B" f l u c t u a t i o n s .  Judging from the p u b l i s h e d  r e c o r d r e p r o d u c t i o n s , the same comment probably a p p l i e s to the t o t a l - f i e l d r e c o r d i n g obtained at Ottawa Strome,  (Baker and  1962). To summarize,  the normal o b s e r v a t i o n  r o u t i n e s and  standard i n s t r u m e n t a t i o n were not designed to cope with the e x t r a o r d i n a r y f e a t u r e s of t h i s a r t i f i c i a l geomagnetic disturbance.  48.  3)  Geographic coverage.  A l l the s t a t i o n s which r e p o r t e d  major ( l a r g e amplitude) and c l e a r l y - d e f i n e d "phase B" a r r i v a l s l i e i n a geomagnetic l o n g i t u d e band about 205° wide (240° to 8 5 ° ) .  T h i s may be suggestive of some s o r t of  broad f i e l d - l i n e g u i d i n g e f f e c t , o r at l e a s t o f some hemis p h e r i c l i m i t a t i o n , although  i t i s probably f o r t u i t o u s - i t  may simply represent the geographic  d i s t r i b u t i o n of s t a t i o n s  having the a p p r o p r i a t e s o p h i s t i c a t e d i n s t r u m e n t a t i o n and advance n o t i f i c a t i o n o f the t e s t .  Bomke e t a l i a  r e p o r t e d h i g h l y i s o t r o p i c propagation  (1963)  f o r the USAERDL  s t a t i o n s (which cover a 105° band i n geomagnetic l o n g i t u d e t o the east of Johnston I s l a n d ) .  A d e f i n i t e answer to  whether i s o t r o p y a p p l i e s on a g l o b a l s c a l e as w e l l w i l l have to await p u b l i c a t i o n of r e c o r d s from o t h e r c o n t i n e n t s - i n p a r t i c u l a r from the S o v i e t t e l l u r i c network with i t s extended l o n g i t u d e coverage. Two i s o l a t e d r e p o r t s which do not f i t i n t o an i s o t r o p i c g l o b a l coverage p a t t e r n remain t o be e x p l a i n e d , but both are of l i m i t e d s i g n i f i c a n c e u n t i l confirmed  by other  observations. a)  A s i n g l e channel  (D) r e c o r d o b t a i n e d by the UK S i g n a l s  Research and Development Establishment  at Ascension  (Geo-  graphic c o o r d i n a t e s : 6 = 8°S, 7v = l 4 . 3 ° W ; Geomagnetic i t u d e V ~ 1°S) i n d i c a t e s a peak amplitude gamma.  The frequency  lat-  o f under 0.5  response of the system i s roughly  49.  l i n e a r between 0.03 and 2 cps.  However, there i s some p o s s i b i l i t y t h a t the  e f f e c t i v e response of  t o r a p i d f l u c t u a t i o n s may be low because  abnormal pen response  munication) . of  and 0 . 2 cps, with 3 db p o i n t s at 0.007  l i m i t a t i o n s (Stevens, p r i v a t e com-  I n comparison, H and P geomagnetic r e c o r d i n g s  "phase B" obtained a t two other e q u a t o r i a l s t a t i o n s ,  Huancayo and Jicamarca  (both a t A ro 1°S), J  tudes comparable to those obtained a t h i g h e r (Casaverde  et a l i a ,  1963).  indicate  ampli-  latitudes  However, the i n d u c t i o n magneto-  meters a t these two s t a t i o n s were r e c o r d i n g H (magnetic whereas D (magnetic b) V  A telluric  E-W) was recorded a t Ascension,  recording at A l e r t  (6 = 82.5°N, A = 62.5°w~;  = 86°N) f a i l e d t o give a measurable response  Whltham, 1962).  D e t e c t i o n s e n s i t i v i t y o f the  a t i o n i s a few mV/km, and response comparison, a t e l l u r i c Zealand,  N-S),  (Caner and instrument-  time about 1 second.  In  "phase B" r e c o r d i n g a t L i n c o l n , New  exceeded hundreds o f mV/km ( G i l l ,  1962).  To judge  by the p u b l i s h e d r e c o r d r e p r o d u c t i o n s , the amplitude may have exceeded 1 V/km.  S i m i l a r l y , on t e l l u r i c  recordings  obtained a t P r i n c e A l b e r t , Sask. ( 6 = 53»2°N, X = 105.9°W; V  = 62°N), the amplitude  i s w e l l i n excess o f the 30 mV/km  f u l l - s c a l e range (Graystone, the amplitude  1963).  At Meanook ( V = 6 l . 8 ° N )  probably exceeded 100 mV/km (Cook, p r i v a t e  communication).  I t should be p o i n t e d out t h a t the  r e c o r d i n g was obtained on a f i e l d survey  (Law  Alert  et alia,  not as p a r t o f a r e g u l a r o b s e r v a t o r y o p e r a t i o n .  1963),  It i s  50.  consequently  of l i m i t e d r e l i a b i l i t y ,  because of the i n s t r u -  mental u n c e r t a i n t i e s i n h e r e n t i n temporary i n s t a l l a t i o n s . Normally, s t a t i o n s which do n o t r e c o r d any s i g n i f i c a n t e f f e c t s do not p u b l i s h " n e g a t i v e " r e p o r t s .  However,  the l o c a t i o n of other p o s s i b l e " b l i n d s p o t s " c o u l d h e l p t o r e s o l v e the a m b i g u i t i e s between the proposed mechanisms. F o r example, i f confirmed  by other r e p o r t s , the absence of  E-W components i n the d i s t u r b a n c e permit  s i g n i f i c a n t deductions  at e q u a t o r i a l s t a t i o n s would  t o be made about the h o r i z o n -  t a l p o l a r i z a t i o n of the d i s t u r b a n c e , answer on the nature  and c o u l d p r o v i d e an  of t h i s d i s t u r b a n c e .  The need f o r  more three-component r e c o r d i n g s i s e v i d e n t .  Alternatively,  c o n f i r m a t i o n of a gap a t very h i g h geomagnetic l a t i t u d e s  ( > 8 0 ° ) would be s t r o n g evidence f o r a broad f i e l d - l i n e guided mechanism r a t h e r than an i s o t r o p i c e.m. wave. We would t h e r e f o r e be very i n t e r e s t e d t o hear from s t a t i o n s with a p p r o p r i a t e  instrumentation  (time r e s o l u t i o n  1 second o r b e t t e r , d e t e c t i o n s e n s i t i v i t y of a few gammas, frequency  response t o about 1 cps) which d i d not r e c o r d any  s i g n i f i c a n t p u l s a t i o n a l a c t i v i t y at H+2 seconds ( i . e . a t  0900:11s U.T. on J u l y 9, 1962).  I d e n t i f i c a t i o n o f "bs" o r  " c r o c h e t " type events on standard magnetograms i s not d i r e c t l y r e l e v a n t s i n c e the l o n g e r - p e r i o d "main" phase i s probably  due t o e n t i r e l y d i f f e r e n t e f f e c t s ,  charged p a r t i c l e d r i f t s  Maeda e t a l i a ,  1964).  i n particular  (see f o r example P i s h a r o t y 1962, and  51.  APPENDIX I I X-RAY IONIZATION AND ALFVEN VELOCITIES BELOW THE DETONATION POINT  In a d i s c u s s i o n of the d i f f e r e n t mechanisms i t was p o i n t e d out t h a t the p r o p a g a t i o n time of a hydromagnetic wave between the d e t o n a t i o n p o i n t and an a l t i t u d e of 80  km  c o u l d not be a c c u r a t e l y computed because of the I o n i z a t i o n i n c r e a s e below the e x p l o s i o n .  However, some l i m i t i n g  v a l u e s can be d e r i v e d , s i n c e the main prompt  ionizing  e f f e c t s over t h i s path are due to x-ray energy d e p o s i t i o n . There are two major u n c e r t a i n t i e s i n the parameters used f o r computation of these e f f e c t s :  a) the x-ray  y i e l d , which c o u l d v a r y between 30$ and 70$ of the t o t a l yield,  depending on the type and c o n s t r u c t i o n of the bomb;  b) the x-ray temperature of the r a d i a t i n g m a t e r i a l s , ranges between kT = 0.5  which  kev and 2 kev f o r an u n s h i e l d e d  explosion. Since the energy from h i g h temperature e x p l o s i o n s Is d e p o s i t e d mainly at lower a l t i t u d e s where r e c o v e r y i s very r a p i d  ( L a t t e r and L e L e v i e r , 1963)* lower temperature  d e v i c e s would have the maximum e f f e c t on the mean A l f v e n v e l o c i t i e s over the e n t i r e p a t h .  Consequently an upper  limit  f o r the p r o p a g a t i o n d e l a y can be o b t a i n e d by c o n s i d e r i n g a 0.5  kev bomb w i t h an x-ray y i e l d 75$  of the t o t a l  yield  52.  1050 k i l o t o n s f o r " S t a r f i s h " ) ,  (i.e.  2 k e v and 350 k i l o t o n s . of a l t i t u d e outlined  E  <  Z)  The e n e r g y d e p o s i t i o n a s a f u n c t i o n  h a s b e e n computed u s i n g  b y L a t t e r and L e L e v i e r  " $(ff*  ^tsfr  and a l o w e r l i m i t f o r  the saddle-point  method  (1963):  r ( z ) . [ c . h ( ) f ? exp[Z  where E ( z ) : t h e e n e r g y d e p o s i t i o n  (ergs/cm3)  i[c.H(z)]^ per unit  x-ray  flux kT:  the x-ray  temperature  i n kev  r(z):  the density  h(z):  t h e t o t a l mass p e r u n i t a r e a  at altitude  between t h e e x p l o s i o n  z (gr/cm3) o f t h e atmosphere  and a l t i t u d e  z  and C = 10.2 x 1 0 / ( k T ) 3 3  The  values  o f t h e p a r a m e t e r s r ( z ) and h ( z )  b e e n d e r i v e d f r o m t h e ARDC model a t m o s p h e r e Champion and Pond, The P(z) and  x-ray  M u l t i p l y i n g E(z)  flux  a t any a l t i t u d e  by p ( z )  yield  f o r each a l t i t u d e and s i n c e  2.1  produced f o r each e r g o f d e p o s i t e d  i o n i z a t i o n AN c a n be computed. AN  i s g i v e n by  Figure  gives x 10  energy,  and an x - r a y  yield  1 0  t h e magniionpairs  the r e s u l t a n t  8 shows t h e v a l u e s o f  a t a l t i t u d e s f r o m 50 t o 350 km, f o r 0 . 5  atures  i nkilotons,  i n km, i . e . R = 400-z f o r " S t a r f i s h " .  tude o f the i o n i z i n g p u l s e , are  (Minzner,  1959).  = 3.2 x 108y/R2, where Y i s t h e x - r a y R the distance  have  o f 1050 k i l o t o n s .  and 2 k e v temper-  53.  The of  altitude  The  corresponding  time  km b a s e d on t h e s e  T  m  a  x  min  as a f u n c t i o n  h a v e b e e n d e r i v e d and a r e p l o t t e d  propagation  T  Alfven velocities  d e l a y between a l t i t u d e s  o f 350 a n d 80  velocities i s (0.5  = 46 s e c o n d s - 10.6  k e v , 1050 k i l o t o n s )  (2 k e v , 350  seconds  kilotons).  Some q u a l i f y i n g  comments s h o u l d be made:  1)  i o n i z a t i o n has been n e g l e c t e d ,  The a m b i e n t  time  ion densities  x-ray 2)  ionization  are several orders  In particular,  o f t h e y-ray  tail  region.  o f magnitude below t h e  pulse  energy emissions  neutron  products  has been  and t h e l o w e n e r g y  contribute to ionization  i n this  However, e n e r g y c o n s i d e r a t i o n s and a f e w c h e c k -  computations a b o u t 1-2$  since night-  densities.  I o n i z a t i o n b y o t h e r prompt  ignored.  showed t h a t t h e i r  of the x-ray  c o n t r i b u t i o n w o u l d amount t o  effects,  w h i c h c a n be n e g l e c t e d a s  far  as the A l f v e n v e l o c i t i e s  3)  The s a d d l e - p o i n t method g i v e s a good a p p r o x i m a t i o n  the  values  for  a l t i t u d e s up t o a b o u t  o b t a i n e d by exact  Above t h i s h e i g h t  are  concerned.  numerical  120  km  the divergence  the  exact  rough e s t i m a t e . velocities  this  total  delay  Above  methods  and L e L e v i e r ,  consistently  200 km i t i s l i t t l e  Nevertheless,  to  1963).  becomes p r o g r e s s i v e l y worse,  saddle-point derived values being values.  integration  (Latter  the  time  9.  i n Pigure  lower  than  b e t t e r than a  f o r computations o f A l f v e n  i s q u i t e adequate,  s i n c e a b o u t 60$ o f t h e  i s i n t r o d u c e d between a l t i t u d e s  o f 120 and  FIG. 8  X-RAY  IONIZATION  BELOW  THE  DETONATION  POINT  TEMPERATURE: X-RAY YIELD: (KILOTONS)  0.5 Kev |050  0.5 Kev 350  350  300  250  200 UJ  o Ul  H  20 FIG. 9  ALFVEN  30  40  VELOCITIES  50 BELOW  60 THE  70 DETONATION  POINT  56. 80 km. the  A f a c t o r - o f - 2 e r r o r i n i o n i z a t i o n d e n s i t i e s over  |  r e s t of the path would a f f e c t the t o t a l d e l a y time by a  maximum o f 20$. 4)  No attempt has been made t o even estimate c o n d i t i o n s  j u s t below the e x p l o s i o n p o i n t  ( i . e . 350-400 km a l t i t u d e ) .  The d i f f i c u l t y has been avoided by p o s t u l a t i n g t h a t the p i s t o n i t s e l f was s t i l l d r i v i n g through most of t h i s l a y e r ( i . e . n e g l i g i b l e time d e l a y - expansion v e l o c i t i e s are about  100-1000 km/sec).  The t r i g g e r e d hydromagnetic wave was then  assumed t o have s t a r t e d a t an a l t i t u d e of 350 km. the  Most of  bubble expansion i s upwards i n t o l e s s r e s i s t a n t medium  (Colgate, 1963), and 50 km appears t o be a reasonable e s t i mate of the maximum downward range o f the expansion. 5)  The v a l u e s o f the parameters r ( z ) and h ( z ) are s u i t a b l e  mean v a l u e s , but Johnson  (1961) has emphasized t h a t a c t u a l  v a l u e s a t any one time c o u l d be s i g n i f i c a n t l y  different.  Some check c a l c u l a t i o n s have been c a r r i e d out, u s i n g  extreme  values- f o r these parameters, and the o v e r a l l e f f e c t on the d e l a y time i s of the o r d e r o f ±2 t o 5$.  A further possible  ±1 t o 2$ e r r o r i s i n t r o d u c e d by the v a r i a t i o n s i n the mean m o l e c u l a r weight. To summarize, as f a r as the "minor" sources o f e r r o r are concerned, the d e l a y times should be c o n s i d e r e d  +25$, - 5 $ , i . e . T  T  max = 4 4 - 5 8 min  =  10 -.13  seconds seconds.  57.  A f u r t h e r major u n c e r t a i n t y i s i n t r o d u c e d by shock-wave nature of the d i s t u r b a n c e .  The  the  piston velocity  i s a t l e a s t an order of magnitude g r e a t e r than the A l f v e n v e l o c i t y i n the medium below.  a/a  M = l/\f2  + (a/« )  0  The hydromagnetic Mach number  2  0  where a i s the d e n s i t y behind the shock f r o n t and a  0  u n d i s t u r b e d d e n s i t y (Lundquist, 1952).  i s the  In the absence of  d e t a i l e d i n f o r m a t i o n about the e x p l o s i o n c h a r a c t e r i s t i c s ,  (maximum) v a l u e s of M by c o n s i d e r i n g  can a r r i v e at l i m i t i n g  F o r t h i s case a/a  a s t r o n g shock.  Q  = (7 + l ) / ( 7 - 1) where  7 i s the r a t i o of the s p e c i f i c h e a t s . of  we  The  c o r r e c t value  7 i s not known - an a c c e p t a b l e range f o r t h i s r e g i o n i s  7 = 1.4  to 7 = 2.  The  low values of 7 used by Caner and  Whitham (1962) to e x p l a i n the p o s s i b i l i t y of very h i g h Mach numbers are not j u s t i f i e d , fully  ionized  (1-2$  s i n c e the medium i s by no means  o n l y ) , and s i n c e the shock d i r e c t i o n i s  normal to the d i r e c t i o n of the f i e l d .  F o r shocks normal to  the f i e l d d i r e c t i o n i n a medium where the magnetic p r e s s u r e i s much h i g h e r than the hydrodynamic p r e s s u r e , 7 = 2 used (Montgomery, 1959)  and M = 2.45.  can  At the o t h e r extreme,  the r a t i o of the s p e c i f i c heats up to an a l t i t u d e of 90 i s n o r m a l l y d e f i n e d to be 1.4  1959).  For 7 -  of  m  M to T j _ , we  seconds.  n  1.4,  M = 4.6. an  (Minzner,  be  km  Champion and Pond,  A p p l y i n g t h i s maximum value  a r r i v e at/extreme value f o r T j _ m  n  = 2.2-2.8  58.  I t would appear t h e r e f o r e t h a t f o r bomb  tempera-  t u r e s up t o 2 kev a 2 second time d e l a y i s not i m p o s s i b l e , although not very l i k e l y .  I n p a r t i c u l a r the low x-ray  y i e l d and h i g h Mach number are r a t h e r extreme  assumptions.  F o r temperatures i n excess of 2 kev a 2 second time d e l a y i s quite reasonable.  V  59.  REFERENCES  Baker, R.C. and W.M. Strome (1962). Magnetic d i s t u r b a n c e from a h i g h - a l t i t u d e n u c l e a r e x p l o s i o n . J . Geophys. Res.  67,  4927-4928.  B a l s e r M. and C.A. Wagner (1963). E f f e c t of a h i g h a l t i t u d e n u c l e a r d e t o n a t i o n on the e a r t h ionosphere c a v i t y . J . Geophys. Res. 68, 4-115-4-118. B e r t h o l d , W.K., A.K. H a r r i s and H.J. Hope ( i 9 6 0 ) . Worldwide e f f e c t s of hydromagnetic waves due t o Argus. J . Geophys. Res. 65, 2233-2239. Bomke, H.A., W.J. Ramm, S. G o l d b l a t t and V. Klemas ( i 9 6 0 ) . 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