y Cw -'V*^ as - - H PREPR BSJB Rev. I Lawrence Livermore Laboratory THE SIGNATURES OF THE VARIOUS REGIONS OF THE OUTER MAGNETOSPHERE IN THE PITCH ANGLE DISTRIBUTIONS OF ENERGETIC PARTICLES Harry I.. West, Jr. December II, 19 78 • iwtllj^jl This is .in invited review impel' prepared fur presentation ;iL the Aiierica:l Geophysical Union Ghapman Coef e r ence, "Quant i I a t i vi- Modeling ol Mn^neto.spher i r Processes," 19-22 September 19'/8 at La .lolla, California. u This is a preprint of a paper intended tor publication in h journal or proceedings. Sinc<; changes may bo made before publication, this preprint is made available with tho understanding that il will noi bo cited or reproduced without the permission of the author.
Transcript
y C w -'V*̂ as - - H
PREPR BSJB Rev. I
Lawrence Livermore Laboratory THE SIGNATURES OF THE VARIOUS REGIONS OF THE OUTER MAGNETOSPHERE IN THE PITCH ANGLE DISTRIBUTIONS OF ENERGETIC PARTICLES
Harry I.. West, Jr.
December I I , 19 78 • i w t l l j ^ j l
This is .in inv i ted review impel' prepared fur presentat ion ;iL the Aiierica:l Geophysical Union Ghapman Coef e r ence, "Quant i I a t i vi- Modeling ol Mn^neto.spher i r Processes," 19-22 September 19'/8 at La . l o l l a , C a l i f o r n i a .
u This is a preprint of a paper intended tor publication in h journal or proceedings. Sinc<; changes may bo made before publication, this preprint is made available with tho understanding that il will noi bo cited or reproduced without the permission of the author.
- 1 -
THE SIGNATURES OF THE VARIOUS KECIOUS OF THE OUTER MAGNETOSPHERE IN THE PITCH ANCLE I.JSTKrBUTIONS OF ENERGETIC PARTICLES
Harry I. West, Jr.
Lawrence I.ivermore Laboratory, University of California Livermore, California 94550
Abstract • An account Is given of tlie observations of the pitch angle distributions oi energetic particles in the near equatorial regions of the earth *s Magnetosphere. The emphasis is on relating the observed distributions to the fit-id configuration responsible for the observed effect.!. The observed effect . relate to drift-shell splitting, to che breakdown of adiabatic guiding center motion in regions of sharp field curvature relative to partial gyro r-idii, to wave-partiele interactions, and to movi ng f i el d configurations.
Tut roduct ion
The signature that tfie magnttosphere leaves in the pitch angle distributions (rAD's) uf axitnuthally-drilting energetic particles can be used as an important diagnostic tool in the understanding of the magnetic field conf igurat ion . Tfi is pjper exam I nes these signal: ures primarily emphasizing the PAD's of energetic electrons rather than protons. The reason for this is straightforward. For example, the rigidity Bn for 79-keV electrons, the lowest energy electrons that will usually be considered, is 0.154 ,̂Kj:. In contrast, r he Bp for the lowest energv protons that will he considered, 100-150 keV, is 8 Y % « The electrons are the more useful of the two for probing the fine structure of the tuagnetosphere since in the outer regions of the mag-netosphere the protons are more subject to breakdown of the adiabatic invariants than are the electrons. Of course, in principle, one could use low-energy proton data but then the results are strongly affected by convection.
The effects presented fall mainly into three categories. The first has to do with shell splitting and how the electrons at various pitch angles drift through the distorted magnetosphere; in this case the particle motion is completely adiabatic. The second case pertains to the breakdown of adiabatic motion in those distant regions in which the gyroradius of the particle is no longer small relative to the field-line curvature. The third case pertains to scattering through wave-particle interactions, especially those periods of time when the particles are close to the magnetopause; this case is more difficult to treat theoretically and is less strongly emphasized in this review.
This review relies heavily upon Ogo-5 observations by the Lawrence Li^erraore Laboratory (LLL) experiment during 1968 and 1969 covering the equatorial regions out to 24 Rg [West et al., 1973a; West and Buck, 1974], The experiment consisted o r a 7-channel magnetically-selected electron spectrometer and proton telescope located on a scanning boom. The success of the Ogo-5 data analysis has depended greatly upon the ready availability of good magnetometer data from the UCLA experimenters covering all periods of data acquisition. When appropriate, work other thin our 0go-5 results are cited. Most of the results presented are from dat£ acquired close to the geomagnetic equator. This leaves out
t h e whol e prol j ] <_•::•. ol wha t h a p p e n s t o t h e f i e l d and p a r I i *' I e d i s l r i b u -t i o n s a t t h e e d g e "1 I In- po l n r c a p n e a r t h e e a r t h .t:;<l t h e i n g e u i e i r , m e t h o d s t h a t p ' - o p l e h a v e a p p l i e d in t h e s t u d y o : t o e a s s o i a l e d f i < •] d t o p o l o g y . F'>r f-z.inij'] '-, t h e r e I S t h e u s e of t i e - s o c ' l l l c i ! " t r a p p : n;p
b o u n d a r y " wl i i fh h ; r . Iifi-n w i d e l y u s e d t o d e l l i e , o s t e n s i b l y , t h e < h a i . / / ' f rom c l o s e d Lo op'-n ! i <• 1 d l i n e s . A I s o , d u r i n g '• ' ' I nr e1 * r t r o n e v - h t •. t h e o b s e r v a t i o n of t r a n s i t i o n i r.nn a d o u b l e t o .1 -.in}'.;*- lo: . ; ; c o n e .1.-, t h e s a t e l l i t e e ; i ; ( . r e d t h e p o l a r r a p s h a s b e e n u s e d f . :< te t i s i ve ] y t o d e r i n e t h e t r a n s i t i o n l o o p e n f i e l d l i n e s ; we w i l l n o t h a v e much f u r t h e r t o s a y a b o u t t h e s e m e t h o d ; ; .
In t h e f i r s t p r l r t 01 t h i s pap . - r we- p r e s e n t t in s t u d i e s t.f I ' M / . , o f on*- :\cl i r ••] o r L r o n s in t h e e ; n . i t o r i,-, I r e g i o n s or t h e rn.ijnii-Losp!ier< f rom t h e u a g n * ' t o p a u s e on t h e d a v i d e ol t h e e a r t h Lo a h o u t 17 l'j. "n t t i . n l g h t s i d c of tin- e a r t h . We f i r s t d i s c u s s how .1 r i t 1 - s h e i 1 s p l i t t i n ; , a l t e r s t h e PAD' s of d r i f t i n g e l e c t r o n s . We t h e n f o l l o w th<- e a s t w a r d a z i m u t h a l d r i f t o i t l l e c l r o n s , s t a r t in ; ; or: t h e m o r n i n g s i d e (,l i h e e a r t h , exnmin i :ig 1 h e i r e n e o i m Lei* w i t h t h e : i .», ' . t ietopause in t e r m s ot d r i f t - s h e l l s p ! i 11 i in; , ••;npha ; i /. i eg t he h i gh~ I a t I t i i de r e g i o n s :i«-ar n o o n , and no t in;.-, t h e • - • • • u l t a n t i - v i l n t i o n oi l ie- PAD's in t h e »-xU-iideii a f t e r n o o n n a g n e t o s p b e n . In t i e - pr'-ni i tin i ght m a g n e t o s p i u r e we >:n:;ii ne PA!) 's d u r i n g q u i e t t i i : ' . " . . bowing lb- - Marked e i l e c t s ol d: ; 1 1 - s h e 1 1 s p l i t t i n , ; .
N e a r m i d n i g h t we siiow s p a t i a l l y - d e p e n d e n t <|iiiet I iiao PAD d a t a w h i c h h a v e b e e n a n a l y z e d in t. er.nK e l t i e l d mode l i ag and p a r t 11.1L- t r a j e c t o r i e s . Nex t we d i s e u s s t h e PAD c h a n g e s o b s e r v e d d u r i 11 >; s u b s Lonns ant! show how t h e s e c h a n g e s a r e u s e d t o i n t e r t h e M e l d eon f i j o i r a t i o n s d u r i rig t h e v a r i o u s p h a s e s of t h e s u b s t u r m . T h i s f i r s t p a r t of t i n p a p e r e n d s w i t h a d i s c u s s i o n of t h e PAD e f f e c t s o b s e r v e d p o s t -:ni dn j g h t .
In t h e s e c o n d p a r t t>f t h e p a p e r we p r e s e n t a p o t p o u r r i of p r o t o n and e j e c t i o n o h s e r v a t i nns , w i t h t h e eniphas i s on t h e s ignn I o r e s t h a t nnv i ug b o u n d a r i e s l e a v e in l h e d i s t r J b u t i o n s o f e n e r g c t i c p a r t i e 1 e.s . We f ir ;~! p r e s e n t a b r i e f p i c t u r e o f o u r k n o w l e d g e o f t h e PAD's o f e n e r g e t i c p r o t o n s t h r o u g n o u t t in- M a g n e t o s p h e r e . We t h e n d i s c u s s t h e o b s e r v a t i o n of t h e . s p a t i a l g r a d i e n t s of e n e r g o l i c p r o t o n s by means of t h e . 'nst~w< s t e f f e c t a n d how t h e i r t e m p o r a l v a r i a t i o n s c a n he i n t e r p r e t e d i n I c r n i s of m o v i n g b o u n d a r i e s , ' i b i s i s f o l l o w e d by t h e u s e of e n e r g e t i c - p a r t i c l e d i r e c t i o n a l d i s t r i b u t i o n s i n t h e m a g n e t o t a i l t o i n f e r t h e m o t i o n of f i e l d - l i n e s t r u c t u r e s t h r o u g h t h e u s e of t h e C o m p t o n - C e t t i n g e f f e c t .
P i t c h A n g l e D i s t r i b u t i o n s of E n e r g e t i c H i e c t r o n s
PAD S u r v e y
We begin with a brief survey of the Lib Ogo-5 electron observations at all local times to provide a framework for what follows. Figure 1 shows the Ogo-5 PAD survey. A few words on nomenclature are in order. We have termed the bell-shaped distribution a normal loss-cone distribution because in the early history of space physics it was the distribution normally expected, since the measurements at that time were mostly in thn near-earth regions; also the distribution is shaped much liki a normal frequency distribution (when presented in a Cartesian plot 0-180 ) and is peaked normal to the field direction thus emphasizing' the term normal distribution. Occasionally in the literature this
h a s hufi ) c.'i I ] e*i! a p a n c a k e d > s i r i h u t I on . Tin* d i s t r ihwt i on *it|»! r t . J n e - i r 9 0 ° p i t c h a n g l e s we r a i l ,, b u t t e r f l y l o s s - c o n e d i s t r i b u t i o n , r e : k r t i u ^ i t s s h a p e ( ) ( : i v s : , 0 - 3 6 0 1 ) in ;i p o l a r p l o t . I t h a s b e e n c a l l e d an a n t i - l o s s - c o n e di fit r i h u t i.i>n wii i cli i s a m i s n o m e r s i n o e t i c ! n s s ro i i f i s u s u a l l y ciDp: v . The b u t t e r ! lv ' i s t r i h u t i o n hn^ a l s o b e e n r a i l e d i ' i | ; , i r -s h a p e d wh i ch seoi;-.s p a r I feu i a r I v t n a p p r o p r i a t e . I ' in. i I I .', vi- h a v e t i n 1
j s o t r n p i c d i s t r i b u ; i o n , a uu s v c ' s . i I 1 * - a c c e p t e d t e r n . I l i w r v i - r , i n r he t o u t c x t of" tlit- work p r e s e n t i d I U T I * , E h.- t e r m i s o t r n p ie d , u s n o t n e c e s s a r i l y r .ean t i , . i t i he l a s s m m - i s t i l l e d w i t h p r c - i p i t a t jn>; p a r t i c 1 c s .
I . f t u s now d i s i u s s 1: i i-.urc 1 . V.V s t a r e w i t h t h e mo.-n i n>\ s e r f o r and p r o c e e d e a s t w a r d fo 1 1 ( :•; i n.' t h e a/, i n u i t h a l d r i l l ul t h e c l i ' i ' i D i n s . In t h e n o r n i n>; s i •••! ui wo ] i nd I he n o m a 1 PAD on I t o Lhe magnet o p a u s e . In t h e e a r l y a f t e r n o o n v e f i n d t h e h u t t - r l l y I'AI) a t e x t e n d e d d i s t a n c e s a n d by d u s k we f i n d LIM- b u t t e r f l y I'M) e x t e n d iny, i n w a r d s t o rt. :i t o / . 5 R.-d e p e n d i n g upon e m - r ^ v . The d a s h e s a t t h e more e x t e n d e d d i s t a n c e s r e f e r t o t h e c r o s s o v e r * ro;jj bur i I T : I v t o n o r m a l ' o r - 7 9 - k e V e I t-c t r u n s , ami I he i n n e r band ol d a s h e s it ' ( i s t o t h e c r o s s o v e r f o r ^ H . ^ - k e V <• l o o t r o t i s . N o t e t h a t t h i s band e x t e n d s a c r o s s t h e e n t i r e n i g h t t i m e . s e c t o r . You w i l l a l s o n o t i c e I ha I in t h e e x t e n d e d ea r l y e v e n i nj; s e e l o r t h e b u t t e r l ly PAD p r e v a i l s w h e r e a s in '!>•• c o r r e s p o n d i n g r e p . i o n par;! m i d n i g h t we f r e q u e n t l y f i n d i s o t r o p y . O b v i o u s Iv t h e d a t a show t i l e m a r k e d e f f e c t s of d r i f t - s h e 1 1 s p I i t t i n g , id in tin* r i o r e d i s t a n t n i g h t t inn- m a g n e t o -s p h e r e we h a v e Liu r i u - c l s of s u b s i o n u s . WV t_*x paint on t h i s l a t e r . Some a s p e r t s o f t h i s s u r v e y w e r e known \>r f o r t o the- '>j>o-5 u l i s c r v a t . i o n ; f o r e x a n . p l e , S e r i imi t s u s , 1966 j and I l a s k e l 1 ' 1969 i hau o b s e r v e d t h e b u t t e r f l y PAD i n t h e n i g h t t i m e m a g n e t o s p h c r e . H o w e v e r , Lhe o b s e r v a t i o n s i n t h e a f t e r n o o n magne t o s p b e r e a r e u n i ( | u e l o o u r Ogo- 1 ) e x p e r i m e n t : , and i t t o o k Ogu- ' ) e i ) : : , . . r v a t i o n s !West e t a l . , 1 9 7 3 a ; West and B u c k , 1 9 7 4 ' Lo p u t L e g e t h e J t ! ie p i c t u r e t o r t l ie Lo ta 1 M a g n e t o s p h e r e . We w a n t t o k e e p t h e s u r v e y in ;;:Ind a s we p r o c e e d w i t h t h e r e s t o f t h e p r e s e n t a t i o n .
Drj_ft-SheJ_J SpeAt'A' ' 1 ' - ' 1. M*2S. I/k'^-s
The idea of drift-shell .splitting was probably put forward initially by ,','orthrop and Teller ; 1960 J but has received major impetus through the efforts of Roederer !e.g. 19671. (Also sec Schultz [1972] for later references.) The particle notion under discussion is completely adiabatic. One examines the drift shells of the particles of various equatorial pitch angles and finds that if he breaks the a-Z-imuthal symmetry, exemplified by the near-earth dipole field, that the degeneracy of the drift paths is removed.
The picture of separation of drift shells is usually explained by examining the drift paths of 90 particles along with particles of small equatorial pitch angle. In the first case the equatorially-mi -roring particles must drift at constant B as shown, e.g., by the data of Fairfield [19681 in Figure 2, thus moving from 9 R E near noon to -6.5 Rr£ near midnight. For the second case we find that in evaluating the integral for the second invariant (I = jf V
/I-B/Bm ds) that I is close to being equal to twice the bounce path of the particle, that is twice the distance along the field line between mirror points. Of course, these particles must conserve the first invariant, also, and thus drift at constant B at their mirror point. Roederer [1967] has calculated
ji.'ins- • -11 I'-,•. I n L :;i- ' ii! '-r I i -ip;- i tig ri-i', i IMP. I :i- •' i a r . - i•• i.ara;!_••:" i y.<-i-by l io- 11 • •; •..- j f i v.- r a d i a ! ;; i aij i. -a I s t h a i wr h--o/o • •(>:.>. , .• -v:-.o i . ; t . - w i t h d i M ' c i o n . In Fij ' . i iro 'i W" • ••• T_ I • • - m r TL :.poi)il i lij' PAD 1:-.. "\ :;<. VI - IV | i m ; ) ' m n n . ( ! . - n c r g y <I.-|.i-:<d.-nrr . • • ' id . -it ! . . r I h-- | fn ; i - , t two I. M u l l - fi.t)(. a-vl 'l. ' i '- ') .i:i'l t " a J . - . M - I .•vj .-nt I. - I. fc'J, wi now P a >',: j ; ; due I •. * ],.-M|H" ' i a ! y,r.' t ha t wh i .'• f I c-i - : i.di- r ad i a t i. m i nf . - r a c I ' w i t h •• 11 r t t'on:, if, t h e ; !a-;;;i.-| : | ' i f i v a s al.nwn f.v 11 J * - rhour . -* i r a l r>-:\: I [ a oi l . v a ' . , ' l a o i m -nifi Kcnni-l I'*?.'. .uid --xpi-r iim-nl a I t a - . u l t s . i t , o . ' . ' . , Lymv, and ' . . " . l i i a - r i l ' ) / ' i I . In I n<- riion- i-/.l .'iitli-.l m.-ij'ii.-r.i-.pii.-iM <\. • H. i.S md 'J.IJ-.J .1 n a r row 111;' of III'- PAD' s v i l l i i n r r o a s i II;-. 1 • n. • r j ' -.- [ • <••.• idi-n ( . '.-.'. h. . .•-• ti< >i , - U L ( - H I ( I M | i n d.-t ..•rmiiii' iln- c i n s i - ci| t in- i - M ' v i bui f-npi .-t t h a i i i i s r e l a t .'d I r, . | ; t in-, i n n .
To mak' ' L)M I r a n s l o n i . i t ion ol il l e f - m - n !'A!' d . i i a t." r l i f i r i . t We 11:..- t i e - r a l r u l a t !•(! n - s u i i . s o f I 'm-d.-r .-r !]')'.,"" in J-ij-nr- <>• -vd 'Hig "•,,-of l . i n u v i I : . • ' : . rhiM-r«-:-i. Wi- r l ,oo :a ih.< s h e l l .-n-:;:. i II>- lh<- c ] i : a t . . r .11 7. 't K,, a t u i r l n i g h t a s Hie p I a< e t o i - i -n-ra t <• t in- PAD and n o l i Lha* ' i.-}- >rl i ! • ] • • ; ; t h a t ar t - t o M l ! t h i s s h e l l c n n e I nun s h e ] i s r rn. .. i :;g i m e q u a l o r a ' noon o v e r t h< r a n g e / . a t o ' ) . 7 i-:,.. The c o r v< " ;pnnd i ag f l u x i - s .it t h r / a r l o u s p i l c h a i e ' . U s c m he o b t a i n e d Iron: t in- P A b ' s 111 ;• ' igur- ' ') 1 r a n s f o r m e d I o t h o e u n a t o r and i nl e r p " I ai ed . ( \ 'o l •• t h a i I !;-• m-ivit I VL- rail ia I Flu:-: ; - rad it-al s , exempl i ; j ed in F i g u r e -'<, l" ;; 1 ii. LIM g e n e r a t i on of tin-. hu t t o r ! 1 y PAH. ) The r v s n J i s a r e shown in r i j , n n V. Fo r c o m p a r i s o n w i t h o u r t ransfor i i i '>d r e s u l t s wo e x a m i n e t h e PAD's f o r S e p t e m b e r 18 in F i g u r e H; Liu-so i i . : ta wi-re arju i roil n o a r in i tin igh t. 0:1 a q u i e t d a y . N o t e t h a i I h e t r a n s J urnetf r<-sa\is o o m p a r e most J a v o i M b l y wi t i i t h e nieasurc;iii>nt.s a t 8 t o 4 U r a t h e r t h a n t h e 7 .4 Kp o:' t i i t t r a n s f o r m a t if.-n. Tlie d i . ^ e r e p a m y can he a t t r i hut t-d t o t l i e t o n p o r a I v a r i a t i o n s in t h e p a r t i c 1 c f Luxes b e t w e e n t !ie two d a y s ( t h o V^T)' :•; . v v i on t h e noon n i e r i d i a n d e p e n d upon t h e d e g r e e of m a g n e t ir. a c t i v i t y) ir.ii d e f i r . i e n c i e s i n t h e Mead [ I 9 b 4 i model u s e d by R o e d e r e r in t h u c a l r u l a -t i o n s .
M a g n e t o p . i u s c S h a d o w i n g
M a g n c t o p a u s e s h a d o w i n g i s an ex t r t r i e v a r t a t i o n of d r i f t - ; T i e l 1 s p l i t t i n g t h a t o c c u r s on t h e day s i d e of t h e e a r t h . I n t h e r e g i o n oi t h e m a g n e t o s p h e r e p a s t n o o n , b e y o n d t h a t c o n t o u r o f c o n s t a n t e q u a l : o r i a 1 B ( F i g u r e 2) t h a t mapn !'rom t h e noon m n g u e t o p a n s e t o J o c a l m i d ' l i g h t , wi f i n d t h a t t h e d r i f t p ^ i h s f o r 90 p i t c h - a n g l e e l e c t r o n s map h a c k ( w e s t w a r d ) t o t h e m a g n e t o | i n u K e . U n l e s s t h e r e i s a s o u r c e of e l e c t r o n s a t r.h m a g n e t o p a u s e ( s c a t t e r i n g f rom o t h e r p i t c h a n g l e s c a n he a s o u r c e ) t h e r e w i l j be n o 90 f l u x e s f o r t h e FAu u n d e r q u e s t i o n . I t i s v e r y e a s y t o
11:- . -i i . *. \:r> •.••rt.-Si. •<: <. r,, ] < : ! • : . • .. : i . 1 i 1 : 1 • !<: 1 ^ 1 ^ s - . - : i : . i . r > <•! - . < : : -> t a r . l . - • ; • : ; ] ; . • : • i . ' l - ; : , . . ! ' •• ; . . i ' p l i s ! ; , f i - r M I -1 • •! w ! , i i . M s ' i r . ; : . i r
• T - u i : ; : • • : [ . ; • . ; r , r . p . , : , • . • [ • • i , , • • : . 1 . - • « . - • p m . - l •. •• i ; i , : : i i ' " . JV. r
Ar ' ii- - ! ' - f i r , - ! r i l ! • • ; ! : . ' w i r - l h - u ' . i n ! 1 ; n<>e:i i ' i l ! n • : • : [ . . d t .! 11 a / . i u 1 (.•>• •,p ;!< r .- 1-t-Vf-::i; ''' !•"; 1 in- ' . I'i.A i-p-- ' Mini ft" I - r a n i ' h p r i n t s , i l i - p . - n u i : i c u p o n >. •: -i.-i ' i r i . i l p i U ' h . n - J " , w i . i . - l i :: ,••/.-. ; l , , i : - n . M ' I ' j - u s o u l l . a w . i v ! r . "1 ! : : • • . - ; • : . ; • s r C M "• :.••:,• '.;,'• r - •; a n : . . - • • . . f ' . ' u ' !• 1 i 1.11 i i : :'::<• i m d '. . i 1 • 1 1 i-d . . a ; ' i . . - L n s p : i ' - r •• U P : . ; • . : - . J : : I - V. a ; i : u s - ?: : h i - M o i d I O > O 1 . . V Y ; ; .<- r p . 1 - . - , 1 - s ( ; i c > -pi--." • •! . J S '- . i t ; ' •* •• i 1 ' .' i t - . i - . 1.1 \ ,• .'A A l l - r s i ' u . i t i . r . i i i t ' p . 1 i ii* • >•:* ' h a t : ' -u M > -t- ' , ; i V : r i . M t I s : . . . ' . ' • «• it ' i n - h r r i c h p n i ' ; i . I I ,
p S ' t s r s - v . - l i . i ' . v , l : . « a , i s , t ; a i t i ' - | . I s . 1.1c i \\y ! i :»-i a m ! l r n h •-!', I i i - ! . i i i ! . . . 1 l i r - s i ' i i n / ' ' . • • . , n i • n;-- i'. u . r : a . . , v i l l i M I L - .- i r r m \n. i n i 1 r w a n i l;i<- ,^ - i i : .::>:'. t i . , - p i a l - > r . i i n 1 t n r o t s r r t o w a r d i n . - i ; i r l ! s ' f in v . i n i ' : M 7 -!'. •-;; : ' ) .1 •- : . v s : • i I s !. ' i -v t I .1 i t in!i in : i r I ih- 11. KIM Ilk C i d i .11. .
'Hi . - , s . r : : . . ] - ' s , . I l . - . j j ' . t j . , K, M. ' l u . - K h a - : . a ! ' " ' 1 . t o d : . • • : • • " I t i n s . . -r i r i I ' " t ! . . ' s : > ; - . , • i n s • ' M I V . I I i a n l ! s n I s ; i n a •••>(!.• 1 I ; . i d a l l i r ! i !'••: : < ; : - > . ; : , ' .• < a i ! • - : p a r i i . I -- :: - [ : . • • ] i n s a o w t h a : t !••- ( q u n t o i a n d ii '-. I ' . i i - ' -1 i ' •: '• r i • .• . • T. . . i r ' i 1 t - • / • • ! . •.' i s ' t v i n : : m r l • ' ; I S M " 1 •• I V : . M 1 I s w n " i . ' p i - • • ; • ' . : • •: a I a : l <- ; i ' i s :• r<-i i ;>•,'. I'-'i. '--., ] *' 7 • . I-' i • • • i n i n : . ; : . i w s rcy.u ! I s • :>r I ;:• <.', •• •;!:•! ' . ' a p ' 1'* /•'. ;'.. ; :'.'.i- '. i • ' !<• i d n . ; o i . i !n- p a r I ) r ; •-s •.-'•!• ; i r i n ! /<) «iv..r, • n .-1 I C H P S o n I !n- i • | i i a t n i ' i i r ' p . a : . > i i a I \. \ I c Ii .Mi'.-.i<": <-! / ' J , ' ' » , h i , , . s d M'J a l r a d i a l d i •. L a n . «•:. e l ' , ' . '» , H I , 11 . ' n d I ? :<t . P a r t i " !••• n i - . i r ' ' [ ) p i l ' d i a n p , ! - - . d r U I >> M M - i - ia i . in- i o p a i r n - i n
t>i- I - - ! a s . i n 1 : r r i .-• tl M.n l . - r " . ' M I ' . I K ' I - ' J J . - H I ' ,_• s f i a d ' <v. i n / , , " a m i ( h o s - - w i i . I i i ' r | u ; i t ' i r i ; t ] p i ! ' ' h a n : - 1 t s I i s s s I n a n 0 fi i; i* i I I L Ii n > u , , h : m o n ;... I I i n r f tii-I h i n . a p m a o : . p l i i . ' .
i* i y,y\rv !( l • • ; I : IV.JS m i 1 y l i i c n > M r - : ; ] a i ; n - a i - f i a n s t ' m i r r o r p u i n t s u. f l \:c r"..;:«•( l i v p a r l i r i i : ) ; r n ' i p s . lit' rt- Wi- nnLc t i i a l h i r CJ. 5 ai.d 10 R|.-, t lx-70 :; i t r l i - anu , ! c p a r t ic \ K.--., AW ;\\\ r r o r i n>>. f IOHI* Lo bnl. j u s t i n.s i d f l i u maj'ni t - o p a n s c , v h i - r r a s : n r i ] and i 2 \<y_. tin.' 7 0 J part i cJ cs do not rcnch l iiis |.o int in spac- iiav \ny. *.-m-« MIII t: t- r< *<f y\u- mn^ni-'t'opaus^ car i i e r . 'I'h LS alJ iTKs-uis that Lho.ss par t i i • I cs are srn i Lcred profcrent ia 1! v by encounters witii the vavi.— ri eh n-^ion near the ma^noLopnuso and are los t from our d' sLr ibut ion of d r i f t i ng par tu- le ; : whereas the S3 pi tch-angle p a r t i c l e s are subject to lis:; s c a t t e r .
Ctjnl irnuit i on nf tln-se i ik-as mines f rt.tni exam in ini; etjuator i a I PAD1 s in !he afternoon ria^nuluspherc a l t c i the various dr i f t s i i . l l s have re assembled. Some .strikin;.; r e . u d u are shown in I'ijMivo 9, center vwo panels. Near l.'ie inagtiL LOj.vu.si' we st-t- si mp 1 e magnet opa use shadowing as d iscussed ear] ier» but inwa n\ a b i t we fine PAD's wltli nin ima near 65° as predicted by our model. Fit',tire 11 shows a r ad ia l p ro f i l e of the different pi tch-an^le. K renins for the. da fa on t h i s day. The extent of the region in which j ( , (shown here as j ^ j , the flux at 50'' pi tch angles) is greater than j increases as we exam Lne radia l data acqM ired l a t e r and l a t e r in the afternoon ma^nctosphere. The region of c ross over, j = j , , , fellows roughly that ronstant-B contour vhicli maps from the noon magnetopaur.e to midnight (sec Fij»uve 2) .
I-* I t'j i r< - \V :.h"v/«: ,J T ' . 'HH.I] I ' j u i i l i t>l d-if i :•.< MM i r<". i . - . . r •!•:•.K on :iov<-i;/..-r J O , I V , 8 , -I |-.ir( ii ul.-,r Iv 'p i i . - i da • ,• a: r..-t I< .. ] : . ^:«- . i v n a t . - d a f*J f h r / » . H e r - w- h-tv* p i n t - , m t V - ; c-rp.-reii '-uJ a r f 1«:;< ; a;.d ' ; a - j !'!u:<, wl . iHi i-. il.<- ;-.i-.^ : .u;< ai -. :i.-il 1 ; . i i - i . ,•.;>..]>•. ' . " ; :-•• Vi , . r ; ; 1 . . n o t e - ; Hif n ' a d u a l i wet ••••}•.<• in i r- i . i i i -i- ; . , ] . r . w a; pr o a - i , th<-:;:"/( ! ! i-r ra<i in i d i : ; [an- <•• t 'u ' I i<l i u;1. t in- i-:n r ,<y~d<-p <ai '•<•;:• < r <>•.-• tV<-r fro::, 1. t o 1 a l f. h i S Kr.
F i ; ' , u r - H sli.jw:. l a t a in -r . - i r^". ' " i n r - i . t i<» 1 ..-ii >t l i r . u n l ' . H**r« wo S'-c d a t a .K-rjin'ri-f! on ::..vc:::l - ; i , f !."e'., 1 w< • • : . : . ' . a ! i < a I in- : -.'.I d i s t u r b e d j i t . r in . i ...» l ' .",a\ I'i- .it t h i . :!••.• a-. ' , " . I '.-:.- . M . ,1-it., p o i r . , i s I ' l oL l i -d I ' . r ; . f i — ..-( ... ' ( M ; - . i: it.:i i ; ; . . ' a . l h ' - *-y,«-v i ..»-i.» -.-an'.n-d (),'(<•[• .in<f f o r i ! , ;il '1 /•••••, •[!,-• Nj.p.-r an I ! . v r .•:]•- . • I- 'j-f. ••! t fa d a t a " o r r e s p o n d t " j . f t he p.-.iM i 1117 .it l'») m ; . 0 '> a n d j ( . I n p r o v i d e ih«-rii ' . iit \it-i ' . pee l i v c t p r o t o n d a t a , HKh-IVt 1<'Y, ;in> i m i u d t ' l ; i h " p r o t o n : , hav-- d r i l l e d t h r o u / . h t !n- n i j ' . h t ' i i v ;i:ap,n-' u a p h ' T . n u l M J ' I | I I - | Wi I he v io} i ' i i ? n..-i^,Ma i<- . i d i v h y t h a t ..i CMI'! ' . <! hn ; h- *- lo<'! ;--nv- a w i r ';.*• v^iv.nvt. ipau' v . i h e m:t < r b n u n d a j v a l lh<- p :« i [< ' ; : , 1-. il ] ' . . '» i-:. w h i c h r o r r i - s p r - n d s t . , t in- ;i;i,-i c t i - p a i i s c i 71 a: n-ri'n-N t w i t h i h<- n a . a a - t •• r : e t I T d a t a .
J j) i •x.-ij'ii N i u:\ ' h>- f • i '•(.(•;!() 1 la I a , in p . . r i i < a ; a r t h e ] . r»\";[ cru-rj'.y < h a n -n e l , '.-.-.• f i n d : h a l h,< | l l n : - : . s show l a r g r e a t i - r l .']::fi. • r.-i i i ~ l u " t u a -linn*-; t h a n do Lin* \. h*x i" , . T h i ' . i-- v i v i d . j»rf»Dt t h a i th» ) ! Iny.vs wcr t ' t l o s f f t o i In- n; •.MifLnp.-iMsr fl? 1 r r »>*. i l n d r d r i l l [ | ,rnii : -!i no. n t h a n wiTr t i n ' j , f l u x ' - : ; . Ano l ln - r i i ) i i - r ' ' > t i m : fa< ..a o) t h e d a i . j ]• i J ia i h«*vi*:id - 1 ' i . ; i K f , , ; lu - ;.. l l i iKt^ ; a:, w.-l l ; r : j_ ' ! . ,> :» • . , i n - wi-»,.l o t u . '.ve e x p e r t t in - i t Mi : :<r ; i n ]>. .•i,-in- hu( i t t .-jj . •.-: |>r. n:< ••:!;£•.-tl t t . ; : . i f - i ! v'r>-ini'/'s in thi* i" it- i d <;<»ni t i '.urat t «.>n t.n v.! i p. on! Ma- j 1 1 •::•;>••-; a •- w (- i ' .
J _L r i -j-' L ( - n ' i l l 1 L „ J t 1 ' ' 1 i j , K " J o s LlJ "•'r''
hot us prorccd ;iz i mt j t ha I ]y in to I In* n ij'jit t i'li'- inai'iH-l iv-phrrr in our vxamnn t inn oi <S;\\ a. I"ii',urc l/i sli<»«s a rn<Ual prut' i \-.- •»- vh>- \ and j B f'laxos Tor Oclohi-r 2 1 , I'^hH, and I-"i);i:ro 15 .show; (an it •.• nnnd in>; PAD's for tliL' lowesL I'tnTi-y flinniu-l (79 la*V) of Liu- hhi. f';.i»-r> : : p f r t r o -mctei ' . Here- wu r ind tha t t h f a ' h V f t s of d r i f t - s h e H s p l i t Linp. a r e very s t r o n g . This was an I'^pi-ij ia I ly c|uu-l: day !:iaj;nrLical I v (Kp - 0 ) . In F igure 16 we show a sucoml t'xasnp 11- of qui e f t imc d a t a . Hi esc da< a were actui i red on Sopt '-mhi'r 1h, 19hH, win.1:; O^o "> was inhauiid 1 to 2 hours boTore michn'f.ht duriii)', a vi-ry i<uict i inn- r^ai-nct i\-a I !y (K'p ~ I ) . The corrus;-ondiriji, PADS: were p resen ted e a r l i e r in Ki^ufL- B. So far we have shown only qu i e t l ime da ta In the nif;hLLinie :*• ai;ni'tosphett. . However, even due in}!, suhstorms the hut t e r f ly PA?) ix sec n : u t in 's ta (-,if»n oi space for a l l . but -30 roin before onse t and -10-15 mlii a f t e r o n s e t . During t he se pen" ods i so t ropy u^ual 1 y preva i t s . Sucli qu ie t t imo data in t h i s p a r t of the mngnetesphere is not the norm, more of ten beinp, punctua ted by a substorm or two on such an Inbound pass- However, we now examine the r e s u l t s of a mode Ii n^ s tudy ol quieLt ime data acqu i red i n the midn i g h t mer id ian before proceeding to substorm e f f e c t s .
P_AD*_g Near Midnight — Quie t t ime Modeling Study
On a number of 0go-5 inbound passes near midnight dur ing q u i e t t i m e s t h e PAD's of tlie p a r t i c l e s when f i r s t observed were i s o t r o p i c which wev i
w<!l->vfd by t h e ri . ;uHt\—<U-:-en«!i*nt t r a n s i t i o n t o t h e h«:i I r r t Jy PAO ?;<•.-• r. r t h e e a : M i . Mio ) ow-i i r i d i t y p a r t i c l e s made tin* t r a i ' s i t i o n f i r M :i>;],,vi.-d in t u r n bv '.>*:• h i . - . i n r r i i M d i t v p a r t l r i w . F i g u r e s 17 and 1H :diow twi: u K t r c j i - in t h e kl .ua a c q u i r e d n e a r m i d n i r j i t d u r i n g q u i e t l ir.i-s
V e s t e l ; i l . , 10 TH.iU ' t l i t - Am'.nst-L 1 d . i t a w r r c a c q u i r e d d u r i u j ; a p e r t od ol e n h a n c e d <ivii-iH:i-- p r i - r . s t m -Vest vi a E. , i 9 78n^ whi*. I. "<av . i ccou i i t 1 « T H H - <JJ f ft i'-TT •• i : - [w- , -n :h<- . '«u. ' ,;: ' t-.! and -!! » d a r a ) . I-Vr ea<-h f i g u r e t h e t u p ;i-im-l -.li'-w. t in- i) . : , ' - ' ) !" ii.a--t iv i i r M d a t a in t;SM n - o n l *> r . a t e s , m e a - i a r e d !:v t i n *' ' A rvj i , - ' ' m e n > ; Mu- n i d d l e p a n e l s h o w s Mie scan™ m o d - i l n t e i i il-ii.i ( I 'K ' i t - . ' i ! r v n " / '-. b M T ) , «^ : i i n.-J by t h e M.J- e x p e r i m e n t nn 0-,-r
;' ">; - m b , l '• . ' ' • t l ' u i i p a n e 1 shows a rotndi s k e t c h of :.he ! io Id r, -a! i / u r a r fon j a r • r n ' t i I r ' c i ! M.e d a f a . *M u • A u g u s t - J d a t a s t r ik f IT. I * i •,
nia-U and t l t . i t i s in t h e r e g i o n o) s h a r p e s t r u r v a -l i : i ' ' fm t : t r . d sh . . ' - tS i b a t l o r t in- i a r t i c l e D>t i on • rv.i t i<:i- • I I i r s t aid KI 'C.VHI i n v a r i a n t : - . , . and J ) - r ' » r a . H u ' . ai" I hi- - l c v i v , i : i ! , t o h.- les:-. l!>;'» •]/! '"»
t ; - ::i i:i i:nui;i r . ; ; : • . " . <n cu i 'Va t ui e of ( l ie / j i l d i n p f i e l d 3 i" n< •, in s t a t e d d i ' : ,-r»-ni l y , I.-.-, Mian 1 / Hr ,.i H z d i v i d e d ! v t h e - r a d i e n l of !i in t_ ti-* : c : i r - ! ? s h e . ' \ ! : v-'-- and *-',"i i t iia;=j v r . I Of.-< - ' ! M - i j . - i a i l s <•'. I k - p a r i i -• • 1 ' - " i ' t i <i: i: . Me •• ;r*ji (»• (In- n . - u t r a l -.ii.-rt h.-cv he r t ) •! i . .ctis.a-rl by S p - M . e t "Jf.7 , :"• . 'b . -K. 1- ]«.7! . S o n - t e m p 1<>>V and K "eat WMKI , J U ' " .
l b - t r .xi-ii t i"-) in ?n- .. t n mtuiu I a i i. >n ol I ii#. A n p . n s i - 2 d a t a a l On Vi l"l I t'm d : \ T d i f i , . ; 'a ,' M-a-.n - / h: « .d d.-wi. IN ' u>- n e u t r a l ;.ln'! ' f o r ! ra j<- t t-n'!*-:. -H; t i i id ! : : , • ' . * ; i r t b c r '.!'•'" t i u - . - ay lb and . -.i con: ; . • r va M on •->r L r a i f d • i r i i " , ui, i i . ; d I i u c s r l e . » r ! n Lb-- e a r t h . itn t h i s p a r t i tMi la r da we v;»-r«. a i i ) ' - t .i i d . ' i i t i ! . - l b . - t i a n s i t i n n pa in i . ' - \^r c 1. c' I r o n s in f i v r rri.-irincl ; . 79 i-» x / ; ' : t . v^ ,-,;,,) p r o t e s t : , in t v o vh.'mrn'1 r., JtW)-'»70 k e V . in i - ' j i i i r . ! " ! , v o !••.:• b i . n l o r t h e Au^ns i-'.iri daLa t i n p t i i n t of . - I v U i I a t i - a ;itr : . o - 7b-"; .V , - U - i - l r o t r : was iiun'h t a r t h . - r I rnm t h e e a r t l i Lhan f o r At':1 !: i 2, T h e " i u d i an>.-1 e e h a n j ^ - s i n e o n p . m e i i o n w i t h the . UC(,A :iui;:-.ot i c t i t - Id d- i ta v.vn- ns.-d in a ];•• Mr I in)' s t u d y ' KV-a e[ a l . , J 9 7 8 b ' . U v.: ' . o s i d i ' h ' t o ; i nd a i:iude i w h i c h i ' i t:-- h-.jth a s p e e i s of t h e d a t a <' ' ;! :• v l i , M a t i s : he p a r i i r l e ji i t c b - a r j / l e cb.un;;es an<] - u a ^ n e t i c H e l d v a l u e s . l ' a r t i e l e i:tt»tion in t h e model fi ' ,*ld was Lhen s t u d i e d and Mie r e s u l t s j * . ' ' ^ ' i iw i i» ln t o t h e K i r u c t u r c 'A' Che «,>law.ia s h i r ^ t -
T h e s e f i n d i n v : ; e n h a n c e e - j r i f e - r r c s u i t . s a t .low a l t i t u d e s n e a r t i io t r a p p > a i r . ho imtUr ry . Fr>: L-y.arip! c f F r j t r 19n8 h a s n o t e d a r e g i o n of L s o t r o p y ii'.-.'ii' :ut(in j ^ i i t e v / n d u r i n , ' , q u i e t t i m e s . Imhof e t n l . [L977J l i a v Kiade c e r a i l e r l I'Alj n i ea su rcn i ep t ••: a t low a l t i t u d e s n e a r m i d n i g h t showim ' . p r o f i \v- ui r j j ; i d U y - c k - p e n < ! e n t t r a o s i t L«ns t n i s o t r o p y , be in-4 h i f , h e . ^ l j n r i ; / i d ; t v a t l o w e r - - ; h e l . j s a s e x p e c t e d from o u r m e d e l i n g s t u d y . T h e p r o f i l e ; - i j e r e a c r | i i i r e d a t a v a r i e t y o f m a g n e t i c a c t i v i t y ] e v c - J s , Kp = 2 t o 5 . In g e n e r a ] , t h e h i g h e r t h e a c t i v i t y t h e l o w - t i n
T , - s h ' - ] J was M e m e a s u r e d t r a n s i L i on j ) o i n t , show in; ; t l a t t h e f i e l d was ;r,c=re M i i l H k o f o r C b e s o c a s e s a s e x p e c t e d .
PAD's a t fj.ft t n \> i ' r D u r ! n j ; S u h s t o r m s N e a r Lhe M i d n i g h t M e r i d i a n
The PAD of e n e r g e t i c e l e c t r o n s d r i f t i n g i n t o thu. r e g i o n a t 9 t o 19 Hp ( a s c b y e r v ^ d r;a 0 ^ o - 5 ) n e a r m i d n i g h t d u r i n g q u i u t t i m e s r a n g e s f rom i s o t r o p i c t o b a t t f c r H y . At 9 K}-; > a l m o s t w i t h o u t e x c e p t i o n , we f i n d t h e b u : t e r f l y PAD w h e r e a s a t t h e g r e a t e r d i s t a n c e s , d e p e n d i n g upon j u s t how t a i l l i i - - e t h e f i e i d i s , we may f i n d t h a t t h e i s o t r o p i c
dc iw t h e pci i n t : e I a r e a lo in ' . MM f : • l . • ' • • • • a d i - i b a t i . I <
PAD prevails. The concepts govern i ng the changeover in observed PAD ilu: inj; rpiletlnr.es were ti i :.cussed earlier.
At times, dvnnmie change-; in the field ionfiguration c m dor.iaate the azimuthal oiiects that tin- electrons ;ir.' subject to <n;ring their drill. In |> l/isn^-'ihcri observations in the near-r.ngnef ..t ••• i 1 v (npj:.i:--quanl i t i cs of <-p;- iget i e >• 1 * - * t roiis and prot uii:; ai"<- a! 5i.o*.t a 1 ways 1our.d. Usually, in th<- period o!' a half bout or m belore ;i sobsiorri expansion or onsrt, th- siKi'/.iiftir Ih-ld is oh.'.erved to become more taiilike. 1'n^f that tl.o field rot.H.ion observed only at tin- sa(:t'llit<- imly resells in a more tail like field over a i.tryc reg.'on o| the nngnet o.sphere cn.-.es from the ! a- t (LiL Ugo-j observations show repealed exa"i;; les i>f the transition from the 1 > i J L t. < • r I • y PAD to isotropi' during these gi owl h-phase p.,rind',. Sni.ii- *.; these e* l»-rts are shown in Kip.urt- Hi taken f rnm .Pyttf and We;. I, , 1 *)7y. ;. Her'- we see subst orm ox pans i mi p ha son n.s mar la d at 1701, IvH, i'Oll, 22Y>, and 010r> U'l . Onset was ilr-t ermi ned primarily bv !'i 2 iiii«'r<ipti|s;iLi(tir:, and all but tin* onseL at 19'3'i IT are readily apparent in tin- 0go-r; •»ar!. icJ r ami field (lain. Tin- effects between 20! 1 and 22 y.1 \"T are especially hi! erest hig. Pol low i :i>» onset at 2011 IT the field ln'i:.i:m- more dipolelike. Initially at ens-'., and ibis is always Ibe ca-.e, the PAD's were isotropic but lh»n mi L1 »* • t i mi seale of minutes the but. u:rlly PAD gsadually reemvrged, first at the higher energies (not shown) and later the lower cuergi es. Kivolson a al. ')')',''$') attribute ibis t i-ne dispersion in tlie drift of the electrons from an undisturbed region m the mngaetosphen*. The i-*1 emergence ol the hiiih'rl Iv PAD ibirin.'. (be expansion ir. vivid proof that the field, eonf i gnral :• m, at least Lo tie- west , had become mure d s po1e 1 j ke than that which prevailed earlier. A soul hwa rd turning of the IMF reached the magnelopnuse at ••'..*! n UT signaling (be start of a new growth phase. 1'ossibly the nor mo I recovery el the mngnetosphere to a more ta: 11 ike field may have meant the loss of the butterfly PAD at Ogo '>. In any respect, the new growth phase listened the change of the PAD to tsntmpy wli i eh was acrmupan led by the observat ion of e] ectron-prec ip i ta t ion bremsstrahlung at balloon altitude:; in Scandinavia, Dnrir.;; the next expansion phase, afte'' 2231' UT, the fie It! '.ever became dipnlelike enough an<l/or long enough to allow the hutUrfly PAD to i::vr;;i., Although not too obvious in the data presented here (observational reasons), the? butterfly PAD did reemerge after the 0105-lT expansion. Further examples of substorm related PAD changes observed on Ogo-5 are reported in V.'e-St et al. [197'ibL Pvttu and V!est i\97h- and l̂ -*lte et al. [J976 !.
Baker et al. I 1978 I have made repented ob.seivations o\ PAD's of electrons 30 keV at synebronous orbit in the nipjittinu- seelnr dnrlnn substorms. During qnietlimes tin- normal. PAD was observed, but al.mest without exception the butterfly PAD was observed during the growth to a more taiJJiko field con f ij',urt"it i on in the period prior to snbstorm onset. At onset, the normal PAD returned. Some aspects uf these observations were reported previously by bop.ott and Moscr [1971]. The transition from the normal distribution to the butterfly PAD Hiring the growth phase is marked evidence of tin* appearance of more taillikc fields. The concepts hove been discussed earlier. U'e need the concept of drift-shell splitting coupied with a negative radial gradients in the electron fluxes. Although relatively smooth negative radial gradients
" i ' t c n e x i s t , Liu' I 1 u>: chai'.,;c r.av be more d r a s t i c t h a n t h a i . . Q u i t e o f t e n , we e x p e c t , t h a t d u r i n g s u b s t or ::i g r o w t h p h a s e s t h e f i e l d d i s t o r t i o n s a n d i n w a r d wot i on of t h e may*,nen>pause a r e s u c h i h a t m a g n e t o p a u s e s h a d o w i n g e x i s t s l o r t h e c q u a t o r i. I 1y n.i r r u r in!', e 1 c c t r o n s a s d e s c r i b e d i n a p r e v i o u s s e c t i o n . In s u c h r a s e s t in d r i f t p a t h s o\' t h e s e e l e c t r o n s map we1-- t w a r d t o I.lie m a g n e t o p a u s e a 1 ong eo ' i t . 'iir.s of c o n s t a n t V> s o t h a t :>nlv e l e c t r o n s of s m a l l e r e q u a t o r i i! p i t i ' h a n g l e s a r e s - e t i n e a r m i d n i g h t .
In Fi g u r e 20, 11 q> pain-1 , we h ivr p r o e ided a summary si-:ct ch f o r t h e i d e a s p r e s e n t e d ' u I h i s s e c t i o n . (Tin r e a d e r ::i;iv w i s h t o r e f e r t o P v t t e and West , l ' f /Hi and Wi s t e t a l . l lJ7Ha ' n r i n r t l n - r d i s c u s s i o n of t h e s e i d e a s . ) 'ihi- t o p pa : : e l s l iows [ h e s it u a t a .n t h if p r e v . i i I s ! o r t he ilnt:> o ! b a k e r i t a ] . ]ini>, , t h e lint Lnui two p a n e l s show t h e cnn t . r . i sL inr . s : t uat i o n at. <)-t\t>~ ~>. In t h • t o p p a n e 1 we n o t e t h a t p r i o r t o s u b s t orr.i t h i n n i n g t h e n o r r ,1 PAH p v>--i i 1:,, w h i c h g i v e s w;i\ t o t h e b u l f e r f l y PAM d u r i n g s u h s t o n r . t h i n n i n g . In I he s e c o n d p a n e l we Mini t h e b u t t e r ! Iv PAD d u r i rt;\ tju i. ; t i n e s , wh i ch p i vos wav t o i sol : r o p y d u r i n g , t h inn ing and e a r l v .-xpn*i* i o n . Tn t h e b o l t on p a n e l , at; t h e more e x t e n d e d d i s t a n c e s , n o t e ( h a t i t i s p r o b a b l e i h a ; tin* i s o t r e p i • PAD p r e v n i !:, p r . s u l . M o n n becau: . . - l a i l l i k e f i e l d - ; u s u a l l y p r e v a i l . lb r e t h e h u f t e r t l y PAI-' i s • • "p t 'Ce ' i ! o n l y f o r a p e r i o d d u r i n g rec<»very when the- f i e l d i s d i p o k ' l i k e " r n i i : ii t o -, n|);.(,r t ai! i a b u t ie gu i d i ng c e n t e r mot i o n .
P o s t Mid:i ,',-ht '.< I o I ", R .
The PAIJ fi)i"id at nrrl/v '» to l'j \iy pas t midnight Lo near dusk Lends t ova rd i •:"'. ropy MICWIA. r, in many cases t he PA!) we observe may have a loss c u : 1e but v.v caiviot Lei I) but quite oit.ei] the butterilv effect is observed. Ue have a: lead1.* dismissed the el fects that occur near midnight dur in;; !iof !i quit' and d i .star bed per iods . Dur i ng very quiet per" 1 oris , prohab 1 v act o',:pan ied by low dynami c-pressure of the sol ;ir wind with small oi norihwrd IMF, we can expect the electrons to drift through m i dn ight still ma i at a hi in;; a marked but torfly PAD. However, we not ed that oi t en dur i up, very quiff, t hues, probably in assoc.ia t ion with enhanced dynamic pressure in tin.: solar wind, that the field con-fi'gurut:on could be laiiMke enough fo cause isotropy. Conversely during subst onus, beyond 8 to '1 Kp, we found isotropy dur i ng the growth and ear i y expans ion phases lo!] owed by t he one rgence of the butterfly PAD daring the f iim.-s oi the more dipolar fields.
Although much is known about how the PAD's evolve as they drift through midnight, ve do nut have al! of the answers. Figure 2) shows a rad ial profiIe of scan-nodu1 ated olcctrnn f1 axes obta i ncd on an i abound pass of Ogo-13 near dawn o,i June !b, ] *-J 6 S, a very quiet c into magnetically (Kp - 1 + ) . The PAD forms are sketched on the figure. Figure 22 shows detailed PAD's obtained on this \--;.^\-.. More we find periods of isot ropy interspersed with the butterfly PAD. fucli distributions of PAD's arc common in t h is rep, ion of the mai^netosphore.. However, note that the flux at 90" is markedly enhanced relative to that observed j ust past dusk, Figure IS, in ;.n ec;u i va 1 eat rep, ion premidn Lght. Tt is very poss ib ie that other mocban isms not previously ment ioned are operative. Ass urn? for the moment that the el.ee trons become isotropi c due to the neekod-down field con f i gurat. i on near midnight but only moments later in thai r azimuthal drift are back on field lines allowing
•,;-.] conserv-it j on . At this po i nt, assuming that the part i c 1c motion is still taking place 1.1 the plasma sheet, we find that we have electrons near 90"5 pitch angles drifting faster than lhn.se at low pitch angles [e.g., West et al., 1978bi. The production rate is proportional to the drift rate of electrons at low pitch angles into the isotropizing region, and here we have a .situation which can lead to the evolution of the butterfly effect, in an hour or so of nziniuthal drift. However, this docs not usual ly lead to the very low values of j relative to j P i
seen promidnight. In add i ti on, for the 1 uwer energies v;c expect that electric fields in the nighttime magnctosphore are contributing somewhat to modification of the PAD's.
Prot on and Proton-Electron Assoc ial.ed Observations
General
Most of the pitch-angle effects seen in the PAU's of energetic electrons in the equatorial mngnetosphere have boon seen also for energetic protons. for example, the butterfly effect has been seen at 6.6 K,. by Stevens et al . 1971)! and [iogott and Hoaer I 1971 ], The U.h Ogo-5'PAD observations at 100-J 50 keV show the combined effects of spatial gradients, the butterfly effect, and breakdown of adiahatic guiding-center not ion. Tie.re have been case studies of I hose PAD' s but no syst omnia t ic studies. Ho-vwr, it can he clearly stated that the butterfly PAD exists across th" n ightt i iiiO magnet osphero, but even on quiet days inn-trophy exists fY.cci.rs when the gyro radii of the protons are greater than 1/30 t!u- "inimu™. curvature of the firld lines) much bovond 8 Rj,-. In the inner paf;netr sphere tin- normal PAD exists and flu- efforts there are documented by, ".g. Williams and Lyons ^197'iJ. In the morning magnetosphori. at, su\ , 9 K,, we might expect to see the effects of magneto pause shadow i n g. A 1 1 t'oo often the protons stud i ed from Ogo-5 da ta bad gyro rad j i that wen- too largo to allow traversal of the min imum-B regions wi thoul scattcri ng. Nevertlie1 ess, we have made observations of proton PAD's on disturbed days, that is with a contracted magnetopuuse, in which PAD's similar to Ibe center panel of Figure 9 were observed. There was one major difference, however, and that is 3. strong component of isotropy (near 0 and 1H0') existed in conjunction with the PAD. A strong component of i sotropy appears to be the norm in the PAD' s oi energetic protons i n the extended regions on the days ide. of the earth.
Region of the Hagnotopause
The transition from magnetosheath to mngnetosphore is usually signaled by the change in the field orientation rmd noise and by changes in the plasma-flow pattern. Quite as specific though is the appearance of a double loss cone in the PAD's of the energetic electrons and protons, the electron data being most easily interpreted. Figure 23 shows an example cf an 0go-5 magnetopause crossing near noon. The electron and proton data from the Ll.h experiment are plotted every 4.6 sec as the experiment scanned back and forth at 3°/sec. The zigzag pattern at the top of the figure is the instantaneous pitch angle of the particles read from the scale to the right. For perspective note that peaks in the electron counting rate arc at 90^.
From tV •• magnetometer ye rmn- the maf*netopause crossing at 081? I'T. The spikes in the proton data prior to thai are the signatures of flowing sheath protons [West and Buck, 1976; Roelof et al. » 1976 . The data are consistent wit.li momentary return to the sheath at -0846 and 0851 UT.
In this pass the signature of the transition from sheath to magneto-sphere is relatively cK-ar. "n\.wur, at high latitudes and along the flanks of the mas>netosphe; *•, whei *• the boundary layer is relatively thick, the transition is m a always obvious. This is especially the case when appreriabje fluxes of protons and electrons are observed flowing downstream hi the :: ignotosheath. Fart icularly Rood examples of th' situation nr.Jer discussion arc to be found In Figures J and .'i of West and Unci: 1976 1 showing data acquired on satellite passes niMr dusk.
The gyro radius nl' IO0-1M) keV protons in a ">0-, field is 0.16 Kj?% a si Luat i on wli i ch p'""t .1 i ns to the I'lju.tt or i.i 1 dav:s ide magnetopause . Measurements of j from a : e m u fug spectrometer, such as tin- Li.I, t)gn-r) experiment, ..how asymnet r : es in I he data that are due I f̂ the- fart that with the spectrometer looking westward it measures protons Willi gyro cent'."-'-; 0. *6 Kj,- farther fmni the earth Mian the rmj in I position of the spacer-aft and when looki'im eastward measures protons with gyro centers 1. !' R].- eloser to the earth, a range of [i, V.1 Kj-. Apprec [ abl e proton flux gradients can e.-rm ever this distance, and thus from a single point in spare out can oht a i n a snapshot of the par tic!e d 1strihution. The geometry of tiiis situation is shown in Figure 2b. Kaufman and Konrad; '1973 1 have talon advantage of such efferts in studying magneto-pause boundiry notions. A K o „ Kaufman et al. : 1972] have studied field-line motion: nt L = rj a" high latitudes cm flit- nlghtside of the earth during a magnetic storm. Recently Williams 11978] lias analyzed early I see res\)1 ts usjng three-J incus i onal data from his scanning proton spectrometer. His paper touches on aspects of the previous section as wel] as the east ~w\ -y.l effect.
We have taken advantage af the ens-t-west efioct during the growth phase of a substonn 1 Buck et al., 1973| to study the motion of the plasma sheet in the near magnet ota ii. In this situation the pnrtical fluxes fall off north mid south of the plasma sheet and in a very real sense the particle intensities reflect the field configuration. Figure 25 provides the picture. Hie tipper panel shows typical proton orbits at the rdge of the plasma sheet. The Ogo-5 spectrometer measured these proteus by scanring En the plane perpendicular to the earth's radius vector. (Note that th3 geometry of Figure 24 is idealized; for the ca' e ' n hcir.d the scan pi an is at a marked angle with '.-espect to B.) Since the protons were intrinsically isotropic we were nble t.: use data at all pitch angles which were then ordered in Coras of the distance of the gyro centers fron: the neutral sheet. These results .-re shown in the lower panel as proton flux profiles at different times. Note that ZJJ is the perpendicular distance from 11 at the time of onset of substorm thinning, 0641 UT. The velocity of thinning of the edge of the plasma sheet was inferred from these data [cf. Buck et nl., 19 73 i.
Vela experimenters -Palmer el .11 . , 1 n ?f> have employed a similar analysis in Lhe J ohes nf Lite inaj<netnia i I - 'I hey used proton spat i al gradients measure'! during a snlar particle event to provide the first measurement of field line motions high in the lobes of the n.*u*neto-tail. Obviously l he proton I M S L - W C H I (ffort is ,1 very powerful tool, especially when one \L- limited Lo only one satellite in making observations .
ifoer^et i.c iVoton ,-md Klru-.iron̂ H o w j_n t !n*__ M/i^netotn il
in the la: L section we made use of tin.1 gradients of the parlide fluxes to determine boundary mot Urns. Here we discuss a different Feature in the proton fluxes, the GinipLon-^ot t ing effect, which is important when t he rent er-of-fI ow mot: i on is npproc table in respect vo part it: le velor i t t i-s . Here l h>- obsi-rvi-r sees part ic U s increased in (•nurRV when looking upsLri-.rn and decreased in energy when looking downstream. As a result, nv, anisotrepy appears in the directional distributions if the i-ncry/y spec;ra decrease sufficiently rapid with Increasing energy, '! istnr Hal ly, f'eld line motion in the magneto-ta LI has lie en measured hy means of lo,-.i-energy J1' asma observat ions, ni course, taking advantage of Lhe ';nmpton-GeLl ing effect, Interest ingly though, enerpetie prot^na ran provide such measurements. Recently R o d of et a3 . 114 76! and Keath et al. i!97f>! have used data from the 16-sector SO-200-keV proton spectnui.efer on Imp 7 for sueh measure-i T;nts at 35 iiy down the lai I . Wei I-de fined anisotropics ("airing suh-storms were observed wh irh are readi 1 y inl erpreted as a fl ow. Those data support the rurrent idea of i he format ton of an X-*type neuti a \ 1ine and i ts attendant mot ions.
Raker and Stone f 1') 7h j have made measurements of -2011-keV electrons using their 8-seetor scanning spectrometer on imp 8 at - JO Rj; in the magnetotail. Unlike protons the Compton-Gett tng ef I'eel causes very little an i sot ropy in the count ing rates of encrgeti c el ect rons since the velocities nf the electrons are large, compared to the f Law velocities. Normally the PAD's are isotropic or on occasion show the butterfly PAD. However, Baker and Stone have observed asymmetries in the PAD's of the electrons which are associated with substorms. During substorms they have observed streaming away from the earth suggestive of an X~type neutral lino between the satellite and earth ,in<\ that the observations were being made on open field lines.
Conclusions
Clearly the PAD's of energetic particles that we have been discussing can be used as excellent diagnostic Loo Is in the study of field configurations. AlUiou^ much of what was presented was qualitative, in most cases the underlying theory is well known. Obviously the routine use of PAD data as discussed here, but on a more quantitative basis, is very important in our future studies of mngnetospheric structure.
Acknowledgments. t would like to thank those colleagues who have worked the most closely with mc in the Ogo-5 researches, my immediate colleague R* M, Buck, M. G. Kivelson from UCLA, and T. Pytte from the
-13-
University of Bergen. J mi especial Iv grateful to tin.' UCLA magnetometer exper imentors, P. J. Co! eman and ('. T. Rus.se 1 1 , f or the ready availability of good magnetic field da La. Those field data were essential to the interpret.it ion of the l),-,n-j pa rL icle da La presented in th is revi ew. This work was per i'oi .::ed undc r the ausp ices of tlio l:. S. Depa* tnen t of Eimrgy ev the- Lawrence I. i vendoro l.aborntorv under con'rnct .\'o. W-7405-En.^-43.
Ki-I "creiices
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Kcliu] 1 :'., u . , l l r i I I - i i l i i - l I ; : | i l i t I hi!', .H .1 r i . 1 t r . i rv ; . i l , h .in,-.]. , . 1 . ' . i •; R e s . , 7 7 , fi^.'i, 1 9 7 2 .
S c i - l i n i I s n - ; , P . , l.uw en i - ipy I ' l i - r l r i i i t u in Liu l i r l - i-.ir.ii": n : ; [ i l i r i v , 1. G o o p h y s . R e s . , 7 1 , ft 1 , I9hft.
S h a b a n s k y , V. ! ' . , SIIIIH- pi n n - i s i - s in I lie- III.-II'.IU- I osp lu- I'U , S;..i -i- K< i . Re _!_7, 299, 1971...
S i i n n p r u i i , R. U. O. , A.l i a h a t i i- p a r t i c l e u r h i t s if i •'i.ir.iiol i r n u l l i.iic .1 . ( .uupl-y:;. R e s . , /f t . H i l l , I ' I 7 1 .
S p e i s c r , T . W. , P a r t i c l e m o t i o n in model c u r r e n t .'ill' ' I ' - , 2. A p p l i i i L i o n s Ld a u r o r a s u s i n g a gco i i ia^ne t i i- L a i l mod, -1 , -I. G e o p h v s . K i n . ,
_72, 3 9 1 9 , J 9 6 7 . S t e v e n s , J . K . , E. F . M a r t i n a , anil K. S. Iv ' h i l e , P r o t o n I'liciy.y d i s l r i
t i c i n s from 0 . 0 6 0 t o 3 . 3 MeV a t ft. 6 e a r t h r a d i i . . 1 . G c u p h v s . l u s . , _75, 5 3 7 3 , 1 9 7 0 .
H a s t , H. 1 . , J r . , R. M. Buck , a n d . 1 . R. W a l t o n , E l e c t r o n p. 'Lch a n g l e d i s t r i b u t i o n s t h r o u g h o u t t h e m a g n c l . o s p h e r e a s o b s e r v e d on O g o - 5 , J . G o o p h y s . R e s . , _ 7 8 , 1 0 M , 1 9 7 3 a .
W e s t , H. I . , J r . , R. M. B u c k , a n d J . R. W a l t o n , S a t e l l i t e s t u d i o s of m a g n o t o s p h e r i c s u b s t o r m s on A u g u s t 1 3 , 1 9 0 8 : 6 . Ogo 5 e n e r g e t i c e l e c t r o n o b s e r v a t i o n s ^ p i t c h a n g l e d i s t r i b u t i o n a l in t h e n i g h t t i m e m a g n e t o s p l i c r e , J . G e o p h y s . R e s . . 7 8 , 3 0 9 3 , 1 9 7 3 b .
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! ' is>,. S . i-.jM r > " L i " r ] - r t m n P A D * ' ; ::»•---i-.iir-*-fI h v D j - . '> . ,n M. tn - i i -,(;, I ' j ' . h .
Viw. C>. r r . m - . f m i M i I i m «.! d r i l l • , l i « - I l s I m n t h f n i y i i l '• i d . - t o d . i v . i d . r r r i ; i i* iu- t ( i : .p ! i . -c . - . i ' . .! I • 111; 11 i 'il i : lit - ••dc v>T l ' i - ' i / . C o u w f . * I : , wi r r ; ii. ;•• t h i s l i i ' . n r c l u !« • ! ' - rm i r.i- t i n - d a y s t d . - m i ^ i n s e l p a r r i < ! , . . ..» ,, j ' , i vi >n i ' j u . ' i i n r i . i l p i I i h a n j , I c f o r a p . i r I i n i 1 a r s i n - 1 I a t J . i d \ : - j ; : .
F i v , . 7 . d i ' i i - ' ) M ; i r i - l i - i O i ' l . - c ' U - . . n PAD d a t . i , ' r . . . l - ' i i ya r . - '• t v \u- : n i • • •' I < • ;n i d l! i ; ; i i ! h y i i u - a n s ' i t !>< - r c V f i - r ' :; ' ' a I r n I a t i m i : ; n f d r i I ' -• '.«• I i ' . ; • ! ; • -fin:- in V i f.urr 6. Tin- dashes ,il s:::a . I .i:!)- I *•:; ti-pi.-.«-nl V. ' i , < .-:[;•»;.•• I at ions based • > • i the ilm-dc iv r r.i i en 1 a 1 f .>:y; am! t In an I ho l ':; e ;•:;.< ! a ! ; < m-based "U d a t a .
F:j',. 8. K l c c t m n PA!)1:; in tin- q u i d n i en t l inn- r.ar.nci nspheri- • >n Sep I 1'inl) _-r 18, 1068, as nrnsiiri 'd on Ogo 5. 'I he.se r i s i i l LS an- pt e^-nti-d purl ia I ]y for minpar I son with L lie t ran si 'nrp-il rcsn I i s i n !•' i >:nre 7.
Fij ; . 9. PAD's of LMHTV,('( ic. e l e c t r o n s measured near tin '::ai'.n,-tnpans>.-in the car ly af ternoun on January 7, 19ft9, by Oj-.o r ) .
F i g . 10. Resul t s of f ol lowi nj; I:he d r i f t pa ths of pa r t K 1c s <>! equa to r p i t c h ang le s of 70, 75, 80 and 8 V a t ,1> (^M = 70", s t a r t e d at r a d i a l iji s t a n c e s of 9 . 5 , 10, 11, and 12 Kjr, i nto the h i g h - l a t I tude m iniiuu::i-B reg ions in the noon meridian | liuck, 1975 1. The c a l c u l a t i o n s a re based on t h e Choc-Beard f i e l d model. The i n t e r s e c t ions of the j ; r id l i n e s r e p r e s e n t the mi r ro r poi n t s of the r e spec t ive p a r t i c l e s on the sunward s i d e of the con f igu ra t ion. The conjugate n e a r - e a r t h mi r r o r p o i n t s a re not shown.
F ig , 11. Rad ia l p r o f i l e s ol e l e c t r o n CLuy.es measured in the e a r l y a f t e rnoon on January 7, 1969, by Ogo 5 .
F i g . 12. Radia l p r o f i l e s of e l e c t r o n f luxes on November 29, 1968, measured on O50 5 . This was an e s p e c i a l l y q u i e t day magne t i ca l ly (Kp , 1 ) .
I' i . 1 : . ' • • ' : • y. t i . i t -t .1 ' j i i i l ' n ' . I ' l l '.V i i l l u i i i i l d ; • . [ . • . <•; i V . > : i l l i - a i
: i . i i - i i T . . ; i . ' . : , • : ' . ' , J ' l f . h . l\ • a h n / t ^ | , . i M ; - . • i „ | t „ . i ( . t n ; L l l l j , , ; . , , j , „ ,
'." i ' . " J - ; , " . ; . : i . i! . ; I I n ' : * . i i i • i n d i . - , i t i •• v * : a , •:.-1:i>*i• : r . \ ; • • ' . - • ; • • • • <• " : . : • . : : - [ • : ! •• . : \ V ' . f t •:•• p w r , - r :• , . . , ;<• I i . j - U V . i t - i a ] . , l ' l ' / H j ,
; • : : • : ' I . . * ) i : i - . i ' i . • :> ; . i : ' h i : : . . : : • ->it y.t I - r • , . - * - f i n ; w c i :i . • ! b r . M i i i ••*n
: i r t ! i ' - r . i : ; -" • • •• ••<• r v . - i : i • >:, is• -.j • - / ! :.>• c a r t h . i ; I I *•:j . . ' l a y . M ' f i r a i ; v . V - j i ' u - . - ..' '.•-• - • ' . • ! • ^ r j ; . f ( | " p i , i ' •( i d a y i .
J ' i i * . I - T . I i i ' t l ' - n d a M . ' : * ' j i i r - • ! :Mi , l l l ( ! • • . - ' , i n b o u n d p a s : ; i n ••'if ' r i i : i -
:s ; • .•!; ' ' s n / • . • ; ' ! : t . ' ? , ! 'M..V . v r • , . . - . i i ' 1 ' . ; : = . { ! • I i n ' : . . ' . u l ;:;. n l u h i l h ' l l : l i
I f i - • m m ; r - i t ' - . , ; I 1 : - I M : . [ i i ' . w . M I . l i i - f i ] i - 1 < r I i <'ii <»J M i * <. I c - L r u n : ; .
r . ' i T ' I ' U l r-i- - * I- - I I l i t - :•.'.•:.( - ' I . i t . , I «* 7 « 1 \ p u t s t h f c i m i M m - r i n t h e
iifiit r. 'i ' ; : i ' ' c l '>'•! v c r i i - J brcaf ' IMVII I a rt In r ami c . m s i r v a t i i.n m a i < r (:•• • . i r t ' i -it i ' i' K[ . The :•.-..st e h v h m s d i i l Y n :;••(• lu-Luv.^i t h i s dav and l )•.!? <•! .•'.•;•-• f .' , !•' h'.'a'<- 17, i s t I p • - KMS M h i j ' J i d s o l . i i " w i n d d w i a - h • :<!••••• :> • l . T ' a<- j a l t I T . lav .
I ' i i ' . 1'J. D a t a Imrri a . s u h s l u r r , s t u d y I ' y t t e a n d U'esL, I 0 / S j . Tin-• i-.-m r i ii I 11 at i oi. i "i" I a r k •.; i t ) pi' t h e 0;;o-"> " n r r g e t i r. c L r c t r o n da fa / r o v i d i - s a K'-y t o t in- f i e l d n m i i g a r a t ion ( se t - L r x L ) . a u h s t o n r i o n s e t a s dt-Li.Tr.hu-d hy P i 2 m i c n ^ - i l s a t i o n s v.-ss a t 1 7 0 1 , 1 9 3 3 , 20 U , 2 2 5 2 , and C)|0 r) f;r a s i:,nrki-d.
F i t ; . 2 0 . Si unwary d i a g r a m s h a v i n g t h e PAU's o f e n e r g e t i c e l e c t r o n : ; t.h at; c a n be fxj.---e.ted a t v a r h>':s d i s t anca . - s in t h e m i d n i g h t m a g n e t o -splii-Tt- d n r i in; var i mis p h a s t - s >f s u b s !:< r ; n s . The d o t on v i ch F i g u r e i s t h e o b s e r ' / n ' : ion point. .'.'t-r t t h a t l" t e hJ c o n ! i j u r a t i o n a : e a r l y e x p a n s i o n i s g e n e r a l l y b e l i e v e d t o b e more d i p o l a r t h a n t h e f i n a l f i e l d c o n f i g u r a t i o n .
F i g . 2 1 . R a d i a l p r o f i l e s of s r a n - m o d u l a t e d e l e c t r o n f l u x e s i n t h e e a r l y dawn M a g n e t o s p h e r e a s m e a s u r e d on 0;;o 5 J u n e 5 S 1 9 6 8 . Kp w a s 1 + . The PAD f o r m s a r e s k e t c h e d f o r t h e v a r i o u s r e g i o n s .
F i g . 72. F A D ' s o f e n e r g e t i c e l e c t r o n s on J u n e rj, 1 9 6 8 , i n t h e e a r l y d a v n r r . a g n e t o s p h e r « j . S e e F i g u r e 2 L f o r tin? c o r r e s p o n d i n g r a d i a l p r o f i l e s . See F i g u r e 16 f o r 1'AlV s a c q u i r e d in a r o u g h l y e q u i v a l e n t r e g i o n p r e m i d n i g h t .
Vi;\. '.'.'i. M.i;'ii;-f ! . | j . . u s . < i r . - . - . i a , ' i i M a n " , i i , • ' ' .•-. , ! ; . ! - • i l n < i a v !• . . i K - . - i r - c q u / i t ' . r J a l :-.t,Mi- I f • . p [ , . - r i - . ' I 1 , ' - i r r . l ; t n t ; i \ . ,- ;, : J : . . . - . , • ! •• ,,: !':..-
p a r t i ' k - s l a i n ; ' . ' !«• ' ••< t ' " i i - . , ; i v - " i l.y i :..- / i r . z i . - : - i i i < M I I-. J ! ;" r ,.-; *•..
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!• '!;•. ? ' • . H . - . . I k ' . f ! (•»-.,r...t r v k . r . . V . - r .* i i.,- l i , . a . ' - : . • •.': . t - * • . » . I .;<,<• I l f - r - ' • r " ! " i ' : i n T1 * - 1 r M . 1-- .I i r . T i ' .1:1 . . ; r< :•:;.. r i : • i.t . ; i ; . . 1 t -ir >• v \ ; '• •if -.'inrn-f! I ii r • *" l;'.' J M - M - I . ; r . 1 ; , r i i l ' i ; r , w i l i i ; ' " | . : > . . ; :: r . • ; : > , • ! r-.- '/w - - . tf> 4- . I : . J - . - s i i T . i l t i. • - . i i - . i l v . i - . -! • • : • ( ! •..•:. :.,' : : : , T . ' j i ] < v; - r t i n - •;. a n p l a i n - i j i - i n j ' . t " 1 I . <! . 1 ! .u i . i p ; . ; 1 ' i i M " .<-.\.\\>- 1 • • \ a t : v • I I I .
(••>"}•.. . ' ' , . i .' >>i t i . f ; . . ! • . ! . i t i i-.-r.l - w t - . t « - t : < « f •• •:- I . - r : : , ! : . . ! :\< j i a : ' 1 : , i i i - l Iw.iiu i . i r v - ^ r i n n - , - ! . i r l n ;> , \\v Ui\ti-Vl A « I , , T . : ) . , I ' / C R , -, >i!>;. t 0 r r , . ' I l i i- M p p < T p . , ; ; - I • : | | , .w : . I / p i . . - , ] p r u t Ml n r h i K 1 - T 1 U 0 - - 1 V / , / ' I d - ' . 70 , a : H W O - I ' l V l \a-\ a l i l i c - ' I v " I t h . p l - i - , : : . a ! . ! I . T I ; , l ! ! , . • ; . . . - , : I i m : :,l (.';;•> r j . 'I In- l u w i r 1 . m e I . s h n w . | i f i l i k " : o t t In- w <>l M I 1 I »::•".'•'. • '! «ii ! f e r M i f t i r n c . i i i f . ' M - . - i l f r i r i - i ! a t a a < <pi i m l \>; t i n - 11.1. M . n i i i i i i ) : p t n L m : i p . - I n c i ' l i - r .
NOTICI:
"This report was prepared as an account of work sponsored by the United States Government. Neither the United States nor the United States Dcparlmenl of Energy, nor any or their employees, nor any of their contractors, subcontractors, or their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness or usefulness of any information, apparatus, product or process disclosed, or represents thai its use would not infringe privaiely*owncd rights."
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Marry 1. WL'«L, Jr.
Lawrence LI vet-more L a b o r a t o r y , I hi \ vers I t y o f Ca 1i Torn ia L i v c r m o r e , C a U i o r n l a 94*i50
A b s t r a c t . An account i s >* i von o l t he o h s e r v a l j ims of Lhe p i t ch a n g l e d i s t r i bu t i oris o f e n e r g c t i c p a r i i c 1 es i n the near e q u a t o r ia I r e g i o n s o f t l i t ; e a r t h \s wr j ^m' t f iK f i l i c r i ' . The ewpha.s i.s is on re-1 a t i n>', t he obsc rved d i s t r i b u t i ons t o I he f i e l d c.onf i j ' .nrat i on rcspnn; . i b \c f u r t h e o b s e r v e d e f f e c t s . The observed e f f e c t s r e l a t e t n d r i f t - s h e l l SJJ 1 \ t t In;-,, to the breakdown of ad i aha l i c gu i <l i ii>» c e n t e r inol ion f u r e g i o n s o i' s h a r p f i e l d (.•ui-"-it"re r e l a t i v e t ri p a r t i a l p.yrn r a d i i , u« w a v e - p a r t i c l e i n l < i r a r t lens y
and to moving f i t - I d r u i i l i g u r a l i ons . , . , ^ „ .//, ., „
In i ro t lnc t i o n /
The s i g n a t u r e E h.it Liu- magnetosphcro leaves i n the p i l r h a n g l e d i s -t r i e i U i o n s (PAD's) o| n/.imuLha 1 1 v - d r i I t in} ; oncri ' .et i t: p . . r t i e l i - s can he used as an i inport an I (I i agnos t i i i uo j in the unders J and in g nf t he magnet i c f i e l d con f i g u - a t i o n . I'll i s paper oxami n< :; t h e s e s i ,;na ' u re . ; p r imar i I y ruphasi /. i i ig t he PAD1 s o f em- rge t i e e 1 e r t rons r a t h e r * han pi n tons . The i eason f o r 111 i s i s s i ra i gh I f o r w a r d . For examp I e , L he r i g i d i t y lie f o r /9-k<-V e l e c t r o n s . Me- lowes! energy r - l o e t r o n : : t h a t W i l l u s u a l l y he c o n s i d e r e d , i s O . I V i (\iy. lit e o n ! r a s t , the li. f o r the lowes t eiu-rt'.v p ro ! . .ns t h a i w i t ! he c o n s i d e r e d , 10(1-1 Vt ki-V, i s 8 , 1 ^ . - . The e l e c t i o n s a re Lhe more t i s e i u ! o l the twr> l o r p r o b i n g t he f i n e .st r u c l u re o f l l ie magnetospbere r. i m e in t he i m i i - r re;1, ion*: o f (he Magn e t o s p h e r e t l i e p ro t oils a re more suh j e e t t o breakdown n\~ the ad i a h a l i c i n v a r i a n t s than a re t he e l e c t r o n s . Of c o u r s e , i n p r i n c i p l e , one r m i l d use l o w - o n e r g v p r o t o n da ta bui Lhen Lhe re.sulLs a re s t r o n g l y a f f e c t e d by convect i or i .
The e f f e c t s present cd f a I 1 ina i n l y i n t o t h r e e ca l i-|;t«r i es . 'I l ie I i r s t has t o do w i t h sfie I I sp I f I t ing and how t i le e l e c t r o n s a I va r ious p i l c h a n g l e s d r i f t t h r o u g h t he d i s t o r t e d magnotosphere ; i n t h i s case t h e p a r t i c l e mot ion i s cunipIet e ] y ad i a h a t l e . The second case per La Ins in t he breakdown o f a d i a b a t i c n o t i o n in t hose d i s t a n t r e g i o n s in wh ich t h e j i y r o r a d i u s o f t he p a r t i c l e i s no l o n g e r s n a i l r e l a t i v e t o t he f i e l d - l i n e c u r v a t u r e . The t h i r d case per La ins t o sca t let* i in; t - rough w a v e - p a r t i c l e i n t e r a c t i ons , e s p e c i a 11 y t hose p e r i o d s o i t ime when t he p a ; t t c l e s a r e c l o s e t o t he magnetupmise; t h i s case- i s wore d i f f i c u l t t o t r e a t t h e o r e t i c a l l y and i s l e s s s t r o n g l y emphasized in t h i s r e v i e w .
T h i s r e v i e w r e l i e s h e a v i l y upon O R O - 5 o b s e r v a t i o n s by t he Lawrence L i v c r m o r e L a b o r a t o r y (LLL) e x p e r i m e n t d u r i n g l'J68 and 1909 c o v e r i n g t he e q u a t o r i a l r e g i o n s o u t t o 24 R|,; (West et a h , I 97 ' i a ; West and Ruck, 1 9 7 4 ] . The expe r imen t c o n s i s t e d of a 7 - channe l magnet i ca I I y - s o Jec.tecl e l e c t r o n s p e c t r o m e t e r and p r o t o n t e l e s c o p e l o c a t e d on a scann ing, boom. The success o f t he Ogu-S d a t a a n a l y s i s has depended g r e a t l y umir. I he ready a v a i l a b i l i t y o f good magnetometer da ta f rom the UCLA e x p e r i m e n t e r s c o v e r i n g a l l p e r i o d s o f d a t a acqu i s i t i o n . When a p p r o p r i a t e , work o t h e r t h a n our Ogo-5 r e s u l t s a r e c i t e d . Most o f the r e s u l t s p r e s e n t e d a re f r o m d a t a a c q u i r e d c l o s e t o the geomagnet ic e q u a t o r . T h i s l eaves o u t
