Electron and proton intensities in outer radiation bel

Savenko, I. A.

Shavrin, P. I.

Teltsov, M. V.

Vernov, S. N.

English

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N a t i o n a l  A e r o n a u t i c s  and Space A c i m i n ^ i s t r a t i o n  
G o d d a r d ,  Sparie F l i g h t  C e n t e r  
C o n t r a c t  NO. NAS-5-12487  
t I 
ST - PF - GM - 10516 
THE INTENSITY OF ELECTRONS AND PROTONS 
I N  THE OUTER RADIATION BELT DURING THE PERIOD 1961 - 1964 
\ 
S. N. V e r n o v  
I. A. Savenko 
M. V.  T e l ' t s o v  
P. I. Shavrin 
(USSR) 
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CFSTI PRICE(S) $ 
Microfiche (M F) A 
ff 653 July 85 
1 
22 SEPTEMBER 1966 
https://ntrs.nasa.gov/search.jsp?R=19670003590 2020-03-16T16:52:41+00:00Z
I '  
. 
ST - PF - GM - 10516 
THE INTENSITY OF ELECTRONS AND PROTONS 
I N  THE CWTER RADIATION BELT DURING THE PERIOD 1961 - 1964 * 
Geomagnetizm i aeronomiya, by S. N.  Vernov 
Tom V I ,  No. 4 ,  pp. 658 - 660, I. A.  Savenko 
Moscow, 1966 M. V. Te l ' t sov  
P. I. Shavrin 
S U M M A R Y  
R e s u l t s  a r e  presented of near-equator ia l  measurements i n  
1964 of t h e  i n t e n s i t y  of protons and e l e c t r o n s  with r e spec t ive  
ene rg ie s  > 400 kev and ) 2  Mev i n  t h e  center of t h e  r a d i a t i o n  
bel t .  These r e s u l t s  a r e  compared with analogous da ta  obtained 
i n  1961. 
* 
* * 
Datawere brought f o r t h  i n  the works [ I ,  21 about v a r i a t i o n s  
and absolu te  va lues  of proton and e l ec t ron  i n t e n s i t y  i n  t h e  outer  
r a d i a t i o n  belt  on t h e  b a s i s  of measurements conducted w i t h  t h e  
a i d  of devices  on board t h e  s a t e l l i t e  Cosmos-41[3]. These d a t a  
are r e l a t e d  mainly t o  t h e  high l a t i t u d e  por t ion  of t h e  s a t e l l i t e  
trajectory.  The r e s u l t s  of analogous measurements i n  t h e  near- 
equatorial  zone **are shown below f o r  protons,  r e g i s t e r e d  by 
the s i l i con  n-p d e t e c t o r  i n  the  0.4 - 7 Mev energy in te rva l  and 
of e l e c t r o n s  with energy g r e a t e r  than 2 MeV,  r e g i s t e r e d  by gas- 
d i scha rge  counters  SI-ZBG. 
The r e spec t ive  d a t a  for  c e r t a i n  days of August and Septem- 
ber 1964 a r e  compiled i n  Table 1. 
* OB INTENSIVNOSTI PROTONOV I ELEKTRONOV VO VNESHNEM RADI- 
ATSIONNOM POYASE V PERIOD 1961 - 1964 gg. 
** The s a t e l l i t e  Cosmos-41 crossed t h e  geomagnetic equator i -  
a l  p l ane  a t  t h e  height-26 thousand km i n  t h e  region L-5. 
2. 
K 
T A B L E  1 
Geomagnetic 
environment in the 
previous period 
I 
I Data 
27 August 
28 August 
1 September 
11 September 
3.5 105 
3.1 105 
5.4 lo5 
6 lo6  
cm-2sec-1 
6.4 lo2 
1.3 103 
7 103 
19 
12 
25 
1 5  
Quiet 
Quiet 
31 Aug.22h-2 Sept. 
6 Sept.23h-9 Sept. 
C K=31 
05h, G-stOrm, CK=25 
04h, SC-storm, maX 
The second column of Table 1 shows the intensity of protons 
with Ep>400 kev in the region of space characterized by the values 
of parameters L = 5, B/Bo = 1 (Bo being the value of the magnetic 
field in the geomagnetic equatorial plane), Inasmuch as during 
the time of measurements, the angle between the magnetic line of 
force on L = 5 and the axis of the directed proton detector con- 
stituted~30~, the experimental values were converted to the pitch- 
angle 8 = 90° in the assumption that the anisotropy coefficient of 
the angular distribution is d =  2. Such a value of&was found from 
the experimental estimate of the altitude course on the basis of 
measurements with the help of the same detector[l]. In the third 
column the intensities of electrons with Ee> 2 MeV are figured, 
obtained with the aid of the counter SI-ZBG with a minimum shield- 
ing 0.84 g cmW2, The comparison with the indications of the other 
counter SI-ZBG, shielded by a layer of matter > 3 g ~ m - ~ ,  provides 
the basis to neglect the contribution of bremmstrahlung (in the 
center of the outer radiation belt), The sum of three-hourly va- 
lues of K-indexes for twenty four hours is given in the column 
before the last, preceding the time of measurements, and in the 
last column, there is a brief characteristic of the magnetic en- 
vironment previous to the measurements of [4]. 
It should be noted that a two-week quiet geomagnetic envi- 
ronment (CK = 10 7 15) preceded the measurements of 27 and 28 Aug- 
ust, From 2200 hours (Moscow time) on 31 August to 0500 hours on 
2 September, the ground stations registered a magnetic storm with 
gradual commencement (G-storm). On 1 September C K  = 25 was regis- 
tered. From 2300 hours on 6 September to 0400 hours on 9 September 
a magnetic storm with sudden commencement (SC-storm) was noted that 
led to an increase of C K  to 30 on 7 and 8 September[*’tl*. 
* The sum of the planetary Kp-indexes for the indicated day 
did not differ fromZK bi. 
Detector, 
Threshold Energy 
3 
I,, crn-2sec-l 
The analysis of data in Table 1 leads to the conclusion 
that the geomagnetic disturbances (on L = 5) are reflected sub- 
stantially only in the intensity of hard electrons, whereas the 
intensity variations of protons are gathered within the limits 
of the factor of 2. This conclusion is in agreement with the re- 
sults of the four monthly observations on the satellite Cosmos-41 
in the high geomagnetic latitudes [I, 63. Comparison may be made of 
absolute intensities of low-energy protons and hard electrons in 
1961-1962 (measurements on the satellites Explorer-XI1 and Ex- 
plorer-XIV) and in 1964 (measurements on the satellites Electron 
and Cosmos-41), that is, in a period of essentially different so- 
lar activity. Inasmuch a s  the measurements on various satellites 
were brought forth by nonidentical detectors, the comparison of 
results requires appropriate conversion. By the proton spectrum 
of the outer belt on L = 5, constructed by measurements on the 
satellite Explorer-XI1 of 26 August 1961 in the near-equatorial 
zone[7],it can be determined that the intensity of rotons with 
Ep> 400 kev constituted I F 5  lo5 cm-2sec-1ster-'. Consider- 
ing the conclusion of'[8]that it is more correct to approximate 
the proton spectrum of khe outer belt not by one, but by two ex- 
ponents with different indexes and to make use of the t bles of[8] 
we shall obtain Ip(>400 kev)M3.5 l o 5  cm'2sec'1ster -7 . 
Electron-1, 
Elect ron-2 
~ Cosmos-41 
1 Data Satellite 
5 Aug.1961 
Sept.1962- 
Feb.1963 
Feb. 1964 
Aug-Sept 
1964 
Explorer-XI1 
Explorer-XIV 
T A B L E  2 
1 
The data of the satellite Explorer-XIV [g] may be extrapolated 
on L = 5 by the theoretical curve of[lO]whereupon the intensity of 
protons Ip(>500 kev) is found to be/J2-105 ~m'~sec'~ster-~, and 
that of protons Ip (2 400 kev) a 3. 3*105 cm'2sec'lster'1. 
Therefore, neglecting the significant difference in solar 
activity in 1961-1962 and 1964, the mean absolute intensity of 
protons with Ep2400 kev on L = 5 did not vary. 
4 
The data by absolu te  i n t e n s i t y  of hard e l e c t r o n s  i n  the 
o u t e r  r a d i a t i o n  be l t  maximum, measured on the satel l i tes  Explor- 
e r - X I 1  and Explorer-XIV[g, 11lElectron-1 and Electron-2 [12]and C o s -  
mos-41 are compared i n  Table 2. 
4 
Brought o u t  i n  the las t  column a r e  the values  of e l e c t r o n  
i n t e n s i t y  i n  t h e  o u t e r  r a d i a t i o n  bel t  m a x i m u m  i n  the geomagnetic 
e q u a t o r i a l  plane.  
I f  we take i n t o  account that  for  the per iod  of f ive monthly 
measurements on the s a t e l l i t e  Explorer-XIV, the i n t e n s i t y  of hard  
e l e c t r o n s  of - l o 4  cm'2sec-1 w a s  seldom Observed, b u t  a t  t h e  t i m e  
of  observa t ions  on the satel l i te  Cosmos-41, t h e  ind ica t ed  i n t e n s i -  
t y  exceeded t h e  value l o 4  cm-*sec" only  a f t e r  s u b s t a n t i a l  geomag- 
n e t i c  d i s turbances ,  we  may, on the basis of t h e  da t a  i n  Table 2 ,  
draw a conclusion concerning the tendency toward decrease of the 
mean abso lu te  i n t e n s i t y  of hard e l e c t r o n s  of the o u t e r  r a d i a t i o n  
be l t  i n  1964 by comparison w i t h  1961-1962. 
Considering the noted h igher  d i f f e r e n c e  i n  the v a r i a e o n s  
of a b s o l u t e  i n t e n s i t y  of hard e l e c t r o n s  and low-energy protons i n  
the framework of the formation theory  of r a d i a t i o n  belts a t  the 
expense of the d r i f t  and acce le ra t ion  of charged p a r t i c l e s  from 
the boundary t o  magnetosphere depth[IO],it can be assumed t h a t  t h e  
mean d e n s i t y  of pro tons  w i t h  energ ies  i n  the t e n s  of kev beyond 
the boundary of the s teady  capture  v a r i e s  l i t t l e  w i t h  the var ia -  
t i o n  of solar a c t i v i t y .  A t  the same t i m e ,  the d e n s i t y  of elec- 
t r o n s  w i t h  energy of the o rde r  of hundreds of  kev, forming a t  
d r i f t i n g  of hard e l e c t r o n s  a t  the c e n t e r  of t h e  o u t e r  r a d i a t i o n  
bel t ,  arise s p o r a d i c a l l y  only i n  t h e  per iods  of r e l a t i v e l y  in- 
t e n s e  geomagnetic d i s turbances ,  providing the beginning of the 
formation of "d i f fus ion  waves . ' '[13$4]Therefor~ the i n t e n s i t y  of 
h a r d  e l e c t r o n s  i n  t h e  o u t e r  r a d i a t i o n  belt  i s  sub jec t  t o  long 
p e r i o d i c  v a r i a t i o n  connected with the s o l a r  a c t i v i t y  cycle.  
T h e  au tho r s  thank B. A. Tverskoy f o r  the d iscuss ion  of 
the work and N.  N.  Rachetkin f o r  p a r t i c i p a t i o n  on the t reatment  
of  experimental  ma te r i a l s .  
* * * T H E  E N D * * *  
Moscow S t a t e  Un ive r s i ty  
I n s  ti t u t e  of Nuclear Physics 
A r t i c l e  received on 
4 February 1966 
Con t rac t  N o .  NAS-5-12487 Trans la ted  by 
V o l t  Technica 1 Corporation DIANE A ,  CT3RZANOWSKI 
Washington, D. C. 20036 ANDRE L,  BRICHANT 
S u i t e  606, 1145 i 9 t h  St., X.W. Prlncipa 1 Invest igator  
I 
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NO. 4, 661, 1966. 
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The Intensity of Electrons and Protons in the Outer Radiation Belt During the Period 1961 - 1964

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