U. of Iowa 65-36
Observations with University of Iowa Equipment on Mariner I V
m y - October 1965 (Preliminary Report )*
S . M. Krimigis, J. A. Van Allen, and L. A. Frank
25 October 1965
* Development of equipment was supported i n p a r t by contract
with J e t Propulsion Laboratory 950613; reduction of data i n p a r t by National Aeronautics and Space Administration under Grant NsG 233-62.
in part- Thb work WPB pmformed~or the Jet Propulsion L a w , California Ins+it*+e of Technology, .sponsored by the National Aeronautics and Space Administration un&4 Contract NAS7-100.
https://ntrs.nasa.gov/search.jsp?R=19660009910 2018-07-19T09:27:49+00:00Z
1
1. Introduction
This report continues the presentation of measurements made
with the Trapped Radiation Detector on Mariner IV. For a,descrip-
t ion of the experimental apparatus, the scient i f ic objectives, and
some early results, one should refer t o University of Iowa Research
Report 65-5 of 22 February 1965 [Van Allen, Dimigis, and Frank,
19651.
[Van Allen e t al., 1965a] summarizes some of the resu l t s obtained
i n the period February-May 1965, and discusses the possibi l i ty of
detection and measurement of the Martian magnetic moment w i t h the
Trapped Radiation Detector. A detailed discussion of the Martian
encounter measurements has been given elsewhere [Van Allen e t al.,
1965bl. The present writing i s mainly concerned w i t h the inter-
planetary resu l t s and i n particular w i t h those obtained from the
beginning of May t o October 1, 1965, on which date the transmission
of data was terminated.
In addition, University of Iowa Research Report 65-15
2
2. Operation of Equipment and Data Reduction
A l l four University of Iowa detectors continued t o function
properly through October 1, 1965, on which date the present phase
of the Mariner I V mission ended. The temperature of the package has
declined gradually and i n the expected m e r from the f l i gh t maximum
value of 29.4" C on day 334 of 1964 t o 9.3' C on day 267 of 1965.
The f ac t t ha t the experiment was shut off during picture playback
a f t e r encounter appears not t o have caused any deterioration i n
detector performance.
The data analysis up t o the present time has been done by
using the Jet Propulsion Iaboratory' s "user's program" listings.
From these preliminary data the folluwing papers have been or are
i n the process of being published:
(1) J. A. Van Allen, Absence of 40 keV Electrons i n the
Earth's Magnetospheric Tail a t 3300 Eiarth Radii, J . Geophys . R e s ., E> 4731-4739, 1965.
(2) J. A. Van Allen, L. A. Frank, S. M. mimigis, and
H. K. H i l l s , Absence of M a r t i a n Radiation B e l t s and Implications
Thereof, Science, - 149, 1228, 1965 . (3) J. A. Van Allen and S. M. mimigis, Impulsive miss ion
Of - 40 keV Electrons frm the Sun, J. Geophys. Res., - 70, December,
1965
3
In addition, the following paper was orally presented at the
American Geophysical Union meeting i n Dallas, Texas, September l-3>
1965 :
J. A . Van Allen and S. M. KWrtigis, Interplanetary and Martian
Particle Measurements with Mariner IV, Trans. American Geophysical.
- - Union, 46, No. 3, 532, 1965 (Abstract).
A t the time of the present writing, three Master Data Library
(MDL) extract tapes have been received fram JPL covering days 333-340
and 340-347 of 1964 and days 032-039 of 1965. The quality of the
data i s satisfactory and further tapes are awaiting processing on the
University of Iowa IBM 7044 computer system.
I ‘ I
1 1 1 I
4
3. Solar Events During May-October 1965
' (a) General Remarks
In Figure 1, the d a i l y averages of detectors D1 and D2
have been plotted f o r the entire period of the Mariner I V f l i g h t .
It i s observed t h a t since the beginning of May, the frequency of
low energy solar proton events has increased considerably, compared
t o the November 28, 1964 - A p r i l 1965 period. It is necessary
a t t h i s point t o define what constitutes an "event", -since the
c r i t e r i a for distinguishing different events i s somewhat subjective.
A solar event i n th i s study i s defined as a s t a t i s t i ca l ly
significant departure of the counting rate of the detector from i t s
background level and an eventual return t o th i s level after a specified
period of time, which may vary from a few hours t o a f e w days. A
clear resolution in to dis t inct events is smetimes d i f f i cu l t due t o
complex intensity-time profiles.
Figure 2, where the increase which began on day 163 continued on
t o day 170; i n the qpinion of the authors, two events are involved,
the f irst one on days 163-165 and the second one on days 166-170
A case in point i s shown i n
The various separately identified events and other relevant
I
5
I
information are l i s t ed in TElble I.
are apparent:
The following general features
(1) A t o t a l of 24 solar events has been observed, 22 of which
occurred during the l a s t 5-l/2 months of the approximately 10-month
period of observations.
(2) For the first time, three "pure" electron events were
observed i n association w i t h phenomena on the sun; i n addition, one
event was seen which contained an admixture of protons and electrons.
.
(3 ) It i s seen f rm the last column of Table I that as the
Earth-Sun-Probe (ESP) angle increased, it became increasingly d i f f i cu l t
t o find a plausible correlation between events on the sun and par t ic le
observations at the position of the spacecraft.
(4) Except for the event of February 5, the maximum flux in
the proton events i s much less than the typical flux observed ear l ie r
i n the solar cycle.
(5) Occurrence of the events appears t o be independent of
s o l a r rotation.
Iet us naw examine same of the major resu l t s i n de ta i l .
-. .
6
(b) Electron Events
In Figure 2 the counting rates 105 a l l University of Iowa
On detectors i n Mariner I V are plotted fo r days 145-175, 1965.
day 145, there i s a large increase i n the counting rates of
detectors A and B, with no indication of an acccanpanying enhance-
ment i n the rates of detectors c, D1, and D2.
properties of the five detectors one concludes that the par t ic les
which caused the increase must be electrons of energy > N 40 keV
[Van Allen and XTimigis, 19653 . event occurred on day 156, and another on day 164.
time profiles exhibit abrupt onsets, increases t o maximum values i n
times of the order of a f e w hours, and gradual declines over periods
of one t o two days.
those seen i n solar proton events for proton energies of the order of
tens of MeV. It appears t h a t these electrons are emitted impulsively
from the sun at approximately the same time as are bursts of radio
noise and x-rays observed by others w i t h t e r r e s t r i a l equipment.
By combining the
A similar, although l e s s intense,
The intensity-
These profiles a re morphologiccdly the same a s
mese electrons propagate diffusively i n interplanetary space,
although the i r behavior appears t o be significantly different than
that of energetic protons, i n that the i r diffusion coefficient appears
t o be independent of heliocentric r a d i a l distance [ c f . XTimigis, 19651 .
I
7
It i s estimated that about electrons E > 40 keV were
A i t t e d on May 25 and on June 5, and about e -
on (Tune 13. Such
electrons constitute a new tool for study of the structure of' the
interplanetary magnetic field and fo r discussion of solar flare
physics [Van Allen and mimigis, 19651.
(c ) proton Events
In Figures 2 through 4, four-hour averages of the detector
counting rates have been plotted f o r days 145 t o 274 of year 1965.
We shall concentrate our attention on detectors D and D since
they are the most sensitive ones, due t o the i r l o w background
counting rate; i n addition, the par t ic le identification i s conclu-
1 2'
sive since they are insensitive t o electrons.
(as l i s ted in Table I) were identified by use of the c r i t e r i a given
The proton events
ear l ie r i n section (a ) .
stayed above background about 40$ of the time during the period of
It is seen that the counting r a t e of 9
observation.
on the sun as seen frm earth is tenuous a t best, and could be m i s -
leading, especially at large ESP angles. This i s par t ly due t o the
f ac t that the par t ic le intensit ies are low, and that t h e propagation
mechanism ( i f the particles are of solar origin) appears t o be that
The association of' a particular event w i t h ac t iv i ty
8
of mass motion rather than free diffusion i n a hamogeneous medium.
The intensity-time profiles shown in Figures 2-4 d i f fe r
considerably frm those of protons whose energies are in the tens of
MeV.
The only event which approaches the "typical" proton event occurred
on days 152-156, with a sharp onset and a slow decay; it i s probable
The onset of an event i s usually very slaw as i s the decay.
'that a diffusion model calculation w i l l adequately describe the
The event on days 218-221 intensity-time prof i le in t h i s case.
appears t o be of particular interest; the r i s e i n intensity occurred
i n about three days, whereas the decay from maximum took place i n
l e s s than a day. This behavior i s exactly the opposite of that
expected i n a "typical" event; it suggests that the abrupt decay
may be a spat ia l rather than a time variation and thus implies dis-
continuities i n the medium with a scale of - 10 lan. 6
(d) Interpretation
We have seen that more than 90s of the events in the period
28 November 1964 - 1 October 1965 occurred a f t e r the beginning of
May, when the spacecraft was a t heliocentric distance > 1.4 A.U.
It was a l s o noted that it is very d i f f i cu l t t o establish one t o
one correspondence between f l a re s on the sun and par t ic le increases
9
a t the position of Mariner I V .
the majority of cases, no sudden commencement was observed at the
earth.
the frequency of occurrence of the events; t h i s has been done in a
preliminary manner and the results indicate that there is no single
27-day period encanpassing all cases, but rather a number of 27-day
periods under which certain events can be grouped; for example,
the events on days ll0, 163-165, 191, 218-221 constitute such a
grouping.
addition, a camparison of the occurrence of these events can be made
w i t h the particular sector of the interplanetary magnetic f i e ld
i n which the spacecraft l i e s [Wilcox and Ness, 19651; such a study
can be effected by ccxnparison of the magnetometer da ta and the
par t ic le data froan the respective experiments on Mariner I V .
From Table I it is seen that i n
One can e d n e the data for a possible 27-day period i n
Further study along these l ines is now in progress. I n
With the foregoing remarks i n mind, one may raise a question
as t o the origin of the observed protons. Were the protons indeed
produced at the sun or d id they acquire the i r observed energies i n
interplanetary space? If the former i s true, then the increase in
ac t iv i ty since l a t e &ril could be taken as the beginning of the new
solar cycle.
thermal) par t ic les i n sufficiently agitated plasmas has been observed
O n the other hand, the generation of energetic (non-
w . .. ,
10
in the laboratory, The lnter@,axmtsry medium may be conaidered ruch
a plasmr 4itated by solas activity, Such a suggestion ha8 a3ready
been mde by Perkor [l9653 9~ Marinor obrervatlonr may conrtitute
11
4 . Long Term Rates of Detectors A, B, C
I n Figure 5 are shown the da i ly mean counting r a t e s of the
three Geiger tubes A, B, and C, omitting the high i n t e n s i t y of the
e a r l y February event and the proton and e lec t ron events l a t e r on.
Data are shown up t o day 196.
declined by about 13% from day 340 of 1964 t o day 196 of 1965 and
t h a t the r a t e of B has declined by about 10% (although i n a
d i f f e ren t manner) over the same period. The rate of C has remained
r e l a t i v e l y unchanged up t o day 145 and has since declined gradually
It appears t h a t the r a t e of A has
by about 5%.
The decline i n the r a t e of A appears t o be a temperature
e f f e c t , as shown by environmental t e s t i n g performed a t JPL and
evaluated a t the University of Iowa.
rate of B i s not understood a t present .
(more shielded from low energy p a r t i c l e s ) i s more representat ive
of t he cosmic ray background.
The change i n the counting
The rate of detector C
I ts counting r a t e w i l l be corrected
f o r time var ia t ions and used t o determine a possible he l iocent r ic
gradient i n ' t h e cosmic r a y i n t e n s i t y between Earth and Mars.
The da ta f o r days 215-274 have been computed and fur ther declines
i n the counting r a t e s of a l l detectors a re present . The da ta
i 8 4 I
I I t 'I
12
w i l l be examined i n de ta i l when the complete records from the MDL
tapes have been received.
I I 1 I I I
. .
13
REFERENCES
Krimigis, S. M., An Interplanetary Diffusion Model f o r the Time
Behavior of In t ens i ty in a Solar Cosmic Ray Event,
J. Geophys. Res., - 70, 2943-2960, 19650
Parker, E. N., In terplanetary Origin of Energetic Par t ic les ,
Phys. Rev. Letters, - 1 4 , 55-57, 1965-
Van Allen, J. A . , L. A. Frank, S. M. Krimigis, and H. K. H i l l s ,
Observations with University of Iowa Equipment on
Mariner IV--February, March, April, May 1965 (Preliminary),
U. of Iowa Research Report 65-15, 24 May 1965.
Van Allen, J- A., L. A. Frank, S. M. Krimigis, and H. K. H i l l s ,
Absence of Martian Radiation Bel ts and Implications Thereof,
Science, - 149, 1228-1233, 1965.
Van Allen, J. A . , and S. M. Krimigis, Impulsive Emission of - 40 keV Electrons from the Sun, J. Geophys. Res., -9 70
December 1965.
Van Allen, J. A . , S. M. Krimigis, and L. A. Frank, Observations
w i t h University of Iowa Equipment on Mariner I V November
1964--February 1965 (Preliminary Report), U. of Iowa
Research Report 65-5, 22 February 1965.
Wilcox, J. M., and N. F. Ness, A Quasi-Stationary Co-Rotating
Structure i n the Interplanetary Medium, Goddard Space
F l ight Center Report X-612-65-302.
Et \
4 1 I I I I I I I I I I I I I
AT r - 1.5 A.U. DURING MAY 25- JUNE 23.1965 E S P = 45'
SOLID LINES INDICATE WE-EVENT BACKGROUND RATES
8 30-
=- 0 z w \
z - 3 0 c'
8 1.0-
p a5-
50-
20 n
DETECTOR A - PROTONS- E p L 6 7 0 t 3 0 K ~ V ELECTRONS - E, 2.45 KeV
I
.*I
. *
= I -**, m---1.+.
- -
DETECTOR B - PROTONS- E p 8 5 5 0 i 2 0 KeV . - - ELECTRONS- E e L 4 0 KeV - -
- -
-
DAY OF YEAR 1965
w - m - \
p z - 3 0 0
1.0
0.5
- - - L.0.S. . 5-.
a5-- - -
- I - - - DETECTOR D, - PROTONS 0.505 E p r I I MeV - - - -
I , ! ' * . ELECTRONS-EFFICIENCY< 1x10 ' -
- -
- - - -
I - **it*
'f
c 0
a2-
z * * t
I 1. 1 I I I I 1 I I I I I I I 4
1 SOLAR PROTON EVENTS OBSERVED WITH MARINER IV
E.S P-48" AT r -1.5 A.U. DURING JUNE 23 - JULY 15.1965
.SOLID LINES REPRESENT BACKGROUNO CQUNTlNG RATES ON DAYS !35- 145
1.0 I- * I I I I EeZ150 KeV
DETECTOR C -Ep?3.1 MeV
0.7
0.5
1.0
0.6
1.0
0.7
0.5
I I
1
FIGURE 3
8-22 Jarmr~
5-13 P e b W
20 April
6-8 w 25-28
26 my
27 my
1-5 m e
5-7 Sue
1z-14 June
13-14 SUne
15-20 June
21 June
28 m e 4 July
2-3 July
4-6 Julv 10 July
13-15 July
m meemtion. 15 July-3 A w s t
3-4 A"8x.t
6-9 A w s t
17 August
2631 m s t
m meemtime 1-3 S e p t d r
22-24 Septslber
25-27 SCpt-hr
ny Iws
au
36-44
ll0
226228
145-148
146
147
152-156
156158
163-165
161-165
166-170
1P
179-182
183-1&
185-187
191
194-196
196215
215-216
218-221
23
238243
243-245
265-267
268270
Eel laodric R a d i a l mstaoee
[A.II.)
1-055
1.140
1.383
1436
1.480
1.480
1.480
1.495
1.502
1,514
1.514
1.521
1.529
1.539
1.542
1.j4j
1.550
1.554
1.567
1.569
1.572
1.573
1.565
1.563
Eouth-Sun-Pr&be A @ g h (Wgretsl
+ 1.8
- 1.3
-24.5
-30.9
-40.2
-40.2
-40.2
-43.6
-45.4
-48.7
-48.7
-50.9
-53 2
-57.0
-58.4
-59.4
-62.0
-64.3
-73.9
-76.43
-80.97
-ea.ll
-1w.o
-101.56
4.3 2 0.3
140
0.4 2 0.1
0.74 2 0.2
eo
0.9 2 0.3
1.1 2 0.3
3 2 0.2
58
1.1: 0.2
5
1.7 2 0.5
0.6 2 0.2
4.2 + 0.2 -
1.1 2 0.2
2.1 + 0.2
0.38 2 0.1
6.4 2 0.3
1.4 2 0.2
6.6 2 0.3
0.4 2 0.1
6 2 0.3
0.8 2 0.2 0.54 2 0.1
Rrtinent solar Activitr As Seen Rrm Earth
C l l l B l l 2 flure 6 san., 0810 w c h s e 2+ r m 5 Feb . , 1750 W
class 2 riare 16 April, 0915 W
m e reported
contin- 25 Hay, 2241 VI
ciaas 1 r m 25 Hay, 2240 W
m e
rype IV 5 June, 1825 WP
Class 2+ iUve 9 . m e , 0600 VI
i&ne reparted
class 2 IlnR 15 ,J"", 0736 VI
clam I+ flere 18 June, ogol m
28 June, 1mo W Clas. 21 flure
m e
. None
ClhS8 1+ Ilarr 9 0547 W
m e
m e
None
c1aas 2 r1ee-e 15 August, 0615 W N M e .