June 1966. *Research supported in part by the National Aeronautics and Space. Administration under Grant NsG-233-62 and by the Office of Naval. Research ...
. .
U . of Iowa
66-13
EXPLORER 1 2 OBSERVATIONS OF CHARGED PARTICLES I N THE INNER RADIATION ZONE*
K . L . Ackersonw and L . A. Frank
Eepartment of Physics and Astronomy U n i v e r s i t y of Iowa Iowa City, Iowa
June
1966
*Research supported i n p a r t by t h e National Aeronautics and Space Administration under Grant NsG-233-62 and by t h e O f f i c e of Naval Research under Contract Nonr-1509( 0 6 ) . HGraduate Research Fellow o f the National Aeronautics and Space Administration.
D i s t r i b u t i o n of t h i s document i s unlimited.
f 2
Measurements of e n e r g e t i c charged p a r t i c l e s i n t h e i n n e r r a d i a t i o n zone with two s h i e l d e d , omnidirectional Geiger-Mueller t u b e s flown on Explorer 1 2 have been used t o c o n s t r u c t B-L contours of the omnidirectional i n t e n s i t i e s of protons E > 2 1 Mev and E > 70 Mev f o r t h e p e r i o d P P
16 August t o 19 September, 1961, p r i o r t o t h e S t a r f i s h high-
9
a l t i t u d e nuclear b u r s t on
July 1962.
The v a l u e s of proton
> 2 1 Mev) omnidirectional i n t e n s i t i e s a r e i n s u b s t a n t i a l (EP agreement with t h e p o s t - S t a r f i s h v a l u e s from T e l s t a r 2 and with o t h e r observations.
Upper l i m i t s f o r t h e omnidirectional
i n t e n s i t i e s of e l e c t r o n s E
e
> 1.6 Mev a t t h e geomagnetic
-1 4 2 equator b e f o r e t h e S t a r f i s h t e s t are Jo < 10 (cm - s e e ) a t L = 1.2, 2 1 Mev and > P ranges 1 . 2
34 Mev i n t e n s i t i e s by a f a c t o r of P h i g h e r L-values L September
,> 2.5
-
10 a t
during a. geomagnetic s t o r m i n
1963 have been r e p o r t e d by McIlwain [1965]
[ s e e a l s o Gabbe and Brown,
19651.
Observations during t h e
next few y e a r s of i n c r e a s i n g geomagnetic a c t i v i t y w i l l be of fundamental importance toward i d e n t i f y i n g and understanding t h e predominant loss and a c c e l e r a t i o n mechanisms f o r i n n e r zone protons. A secondary maximum of proton
u n i d i r e c t i o n a l i n t e n s i t i e s , j,,
at L
(40 < E < 110 Mev)
-
P 2.2 on t h e magnetic
equator was observed with Explorer 15 i n l a t e 1962 [McIlwain,
19631. Explorer 1 2 measurements of t h e omni-
d i r e c t i o n a l i n t e n s i t i e s of protons E
P
> 2 1 Mev and > 70 Mev
a t t h e geomagnetic equator as summarized i n F i g u r e s
7
and
8, r e s p e c t i v e l y , show only a change of slope i n t h e equatorial i n t e n s i t y versus L p r o f i l e s i n t h e region
