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V.";UCRL-51385
THE III ELECTRON AND PROTON SPECTROMETERON NASA'S ORBITING GEOPHYSICAL OBSERVATORY 5
(Final Report for Experiment 6)
H. I. West, Jr.R. M. Buck
J. R. Walton
May 29, 1973
Prepared for US. Atomic Energy Commission under contract No. W-7405-Eng-48
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LAWRENCE UVERMORE LABORATORY
UCRL-51385
THE ILL ELECTRON AND PROTON SPECTROMETERON NASA'S ORBITING GEOPHYSICAL OBSERVATORY 5
(Final Report for Experiment 6)
H. I. West, Jr.R. M. Buck
J. R. Walton
MS. date: May 29, 1973
Contents
Abstract . 1
Introduction .- 1
Instrument and Inflight Operation 2
Electron Spectrometer 2
Proton Spectrometer 5
Dynamic Range . ' 8
Magnetic Shielding 9
Pitch-Angle Scan Mechanism 9
Differential Discriminator and Proton Logic 11
Experiment Status and Failure 11
Raw Data Plots 12
Bibliography of Results 17
Reports 17
Talks . . . 1 8
Publications . . . 22
Resume of Results 24Inner Belt 24
Slot and Nearby Outer Belt .27
Pitch-Angle Distributions in the Outer Magnetosphere . . . . . 29
Plasma Sheet Boundary Motion During a Substorm 50
The April 1969 Solar Particle Event 54
The November 18, 1968 Solar Particle Event 56
Highly-Anisotropic Proton Distributions Observed Interplanetary . . . 58
Concluding Remarks 60
Acknowledgments . 61
References 62
-iii-
THE LLL ELECTRON AND PROTON SPECTROMETERON NASA'S ORBITING GEOPHYSICAL OBSERVATORY 5
(Final Report for Experiment 6)
Abstract
The LLL energetic electron and pro-
ton spectrometer on NASA's Orbiting
Geophysical Observatory 5 (OGO-5) oper-
ated successfully from launch — March 4,
1968—until retirement in August 1971.
Data recovery during this time was about
95 percent of the orbit except for the last
few months. The electron spectrometer
used a magnetic field for electron mo-
mentum selection which served also as
an electron broom for a proton range-
energy telescope. The energy range was
~60 to 2950 keV for electrons (seven
channels) and 0.10 to ~94 MeV for protons
(seven channels). The experiment was
scanned relative to the stabilized OGO-5
for obtaining directional information.
Excellent data were taken throughout the
magnetosphere and in the interplanetary
region (apogee 24 Rp). Studies were car-
ried out in the areas of equatorial pitch-
angle distributions, substorm dynamics
arid field topology, particle spectra (time
history), particle spatial distributions,and solar particle events. Excellent
data were available from other OGO-5
experiments for data correlation. This
report covers instrumentation features
that contributed significantly to the
experiment's success and also pre-
sents a resume of the experimental
results.
Introduction
NASA's Orbiting Geophysical Observa-
tory 5 (OGO-5), launched from the East-
ern Test Range at 0800 LT March 4, 1968,
operated successfully for nearly 3-1/2 yr.
Our experiment (E-06) ran continuously
during this period, with most of the ex-
periment working properly.
E-06 grew out of a 1962 experiment
(West, 1965) conducted on the U.S. Air-
force satellite STARAD (1962 |3K).to
assess the effects of the Starfish high-
altitude nuclear detonation on the earth's
radiation belts (West et al., 1965). This
experiment, consisting of a five-channelmagnetic beta-ray s p e c t r o m e t e r ,
worked well, giving three months of
data in the inner belt and high-latitude
regions of the outer belt. Because the
satellite was spinning, we were able
to measure pitch-angle distributions;
this was important in interpreting the
data.
-1-
In general, interpretation of the inner
belt data was hampered by a paucity of
pre-Starfish data. The STARAD results,
along with those emerging from studies
of the outer magnetosphere and the mag-
netotail by other investigators, pointed
up the need for studying magnetospheric
electrons with instruments able to make
unique measurements in well-defined
energy bins. Background effects would
have to be low or accurately measured.
Pitch-angle measurements would be re-
quired, particularly at the magnetic
equator where such measurements can
determine what is happening along the
field line on the time scale of the bounce
period; pitch-angle distributions also are
sensitive to effects at other longitudes on
the time scale of the azimuthal drift.To complete the picture provided by the
electrons, it was evident that low-energy
proton measurements would be needed. In
the OGO-5 experiment, this was accom-
plished by placing the proton detectors in-
side one of the electron-spectrometer
magnets so that the magnet served the
secondary purpose of an electron broom.
Other measurements on OGO-5 com-
plemented our results. Initially, low-
energy measurements were available via
two electrostatic analyzer experiments,
Unfortunately, these experiments met an
early demise. At times, the plasma-
wave measurements of Scarf et al. (dE/dt)
were valuable. However, for our pur-
poses, the most important information
was the magnetic vector data for our
pitch-angle studies, provided by the
UCLA flux-gate magnetometer experi-
ment. These were the major complemen-
tary data we needed for putting together
the physics.
In this final report, we first describe
the experiment's design and operation.
Although no new technology of a patent-
able nature was found, there are some
features of the instrumentation that mayinfluence future experiments. We then
present abstracts of pertinent reports,
talks, and publications. This is followed
by a resume of results. In the resume
we include a discussion of future work
that should be performed using the
OGO-5 data.
Instrument and Inflight Operation
The instrument report by West et al.
(1969) completely documents the LLL ex-
periment. In this final report, we merely
describe the instrument, emphasizing its
unique features and inflight operation.
The experiment consisted of an elec-
tronics package, located in the main body
of the satellite, and sensors on a boom
called the OPEP-2 (Orbital Plane Exper-
imental Package 2). Figure 1 shows the
electronic functional makeup of the exper-
iment. Figure 2 shows the important
features of the spacecraft, whose proper
orientation required that the solar pad-
dles look directly at the sun and the
OPEP shaft point to the earth's center.
Table 1 gives the characteristics of the
energy channels.
ELECTRON SPECTROMETER
The electron spectrometer used two
small permanent magnets for momentum
-2-
OPEP package
Impulse cmd turn on
Analog statuscommutator
Detector leakagecurrent monitors
Impulse cmd turn on
AmplifiersDiscriminators
Logic
»—|LV powerI I I I I ICounting data
Pulse generatorcontrol logic
Impulse cmd Shift register andHV selection
20 time-snared20-bit accumulatorsDigital
commutator
Inhibits for 52 redundant
floating-pointshift registers
digital words
Equipment group switch
Equipment groupOutputgatesEquipment group "2
Status and sync __ Main body package statusAnalogcommutatorStatus and sync "2 voltages, temp, cmds
OPEP status
FLg. 1. Block diagram of the electronics.
analysis (180-deg first-order focusing)
and solid-state detectors for particle
detection (see Figs. 3 and 4).
Accurate evaluation of backgrounds
was considered essential to the experi-
ment's success. The backgrounds for
-3-
Scan axis
OPEP-2
Magnetic field lineshowing trapped particle
Fig. 2. Orientation of the experiment in the sun-earth-satellitesystem. Note that the OPEP shaft always points towardsthe center of the earth and the solar paddles alwayspoint towards the sun. ,r
channels E. and E» were supplied by a
single detector between the E, and £„
detectors. For the other channels, indi-
vidual detectors were used in a multiplex-
ing arrangement. Figure 5 shows how
the multiplexed pulses were handled such
that the respective electron pulses and
background pulses were routed to their
respective scalars. The multiplexing
arrangement, which worked so well for
E~ through E?, was not used for E, and
E- because of the increase in electronic
noise that would have resulted.
An additional factor contributing to
background reduction was the use of
detectors thick enough to stop the. elec-
trons completely (at least for E through
Efi). Thus, a differential window could
be positioned over the peak in the pulse-
height distribution for the purpose of
eliminating backgrounds more effectively
(from bremsstrahlung and protons).
Other experimenters, by contrast, have
used thin solid-state detectors with a
wide window set to count the wide range
of pulse heights produced. While this is
attractive with respect to simplicity, it
results in a greater background, as
proved by an analysis of the background
spectrum.
The background evaluation procedure
worked extremely well for all regions of
space reached by OGO-5, including
measurements in the inner belt and in
-4-
the interplanetary region during solar-
particle events. In both cases, the major
background problem was penetrating pro-
tons. In using the background data, we
determined the sensitive-volume ratios
of the respective detectors (~10 percent)
before flight. These ratios were im-
proved to ~±2 percent through study of
penetrating galactic radiations during
periods of minimum solar activity when
OGO-5 was free from the influence of
magnetospheric radiations. Normaliza-
tion studies were made during 1968 and
1969, remaining quite constant during
that period.
PROTON SPECTROMETER
Proton data were acquired from an
array of proton detectors (range-energy
telescope and single detector) in one of
the electron spectrometer magnets. As
shown in Fig. 4, the array was in line
with the entrance aperture. Means were
provided for estimating the backgrounds
(by interchanged logic between detectors),
but the results were not of the high accu-
racy available for the electrons. The
electron-broom effect, provided by the
spectrometer magnet shown in Fig. 4,
was quite effective. E l e c t r o n or
Table 1. Spectrometer characteristics.
Channel
Electrons
ElE2E3E4E5E6E7
ProtonsP
P2P3P4
P.K*J
T^
Dp
7
Alpha
«1
Energy range
79 ± 23 keV
158 ± 36
266 ± 36
479 ± 52
822 ± 185
1530 ± 260
2820 ± 270
0.10 - 0.15 MeV
0.23 - 0.57
0.57 - 1.35
1.35 - 5.40
5.6 - 13.3
14.0 - 46
43 - 94
<~ 100
5.9 - 21.6 MeV
Geometry
0.180 cm2 keV sr
0.277
0.390
0.605
4.43
8.57 .
3.88
2.06 X, 10"3 cm2 sr
1.3 X 10"2
1.3 X 10"2
1.3 X 10"2
1.25 X 10"2_9
1.72 X 10_o
1.98 X 10 z
~0.6 X 4 TT cm
1.3 X 10"2 cm2 sr
Acceptanceangle(deg)a
7.6
5.9
4.7
3.5
5.3
4.1
2.5
12
12
12
12
12
12
12
omni
Effective full width at 50% acceptance in the scan plane.
-5-
1.726
4.800
Fig. 3. The low-energy electron spectrometer.
-6-
Light baffles - Al
Armco iron
Electrons
Absorbers
Pole pieces'—Gold case
te
\\
JL
rnmog V
3
'yXI
slsS^ • ^1
B
11
II.
IH
|4
\/ f
f t f f J ' l
(
l.C
Fig. 4. The larger electron spectrometer and the proton detectionsystem. The field of the electron spectrometer acts as anelectron broom for the proton detection system. The fieldin the magnet is high enough to bend low-energy protonsabout 5 deg so the true geometry for the small side detectoris greater than the apparent optical geometry.
-7-
u4)
I - HV
z s
- <
Electron+ background pulses
J^-
2"
II
\Preamp
/II
5 VBackground pulses
To detector leakagecurrent- monitors
To scalar
!Background pulses
Electron+background
pulses
To scalar
Fig. 5. Multiplexing arrangement for the detectors in the magnetic electron spectrom-eters. This procedure ensures that the background normalization, oncedetermined, will be constant.
bremsstrahlung background was never a
problem. However, penetrating protons
were troublesome when we tried to acquire
data in the inner belt and during relativ-
istic solar-particle events. The proton
data channels we used are listed in
Table 1. Some other channels were pro-
vided (West et al., 1969), but these were
not properly calibrated or used and will
not be discussed here.
DYNAMIC RANGE
The geometric factors for the electron
spectrometer were near optimum for
most of the mission. For example, the
maximum counting rates for E., E0, and5Eo in the inner belt got to 10 counts/
second, only on occasion. For these
rates, count rate corrections could be
properly made. By contrast, a factor-
of-10 increase in the geometry for E» or
an equivalent reduction in background
would have been preferred for the inner
belt. Larger geometry would have been
desirable, at times, in the magnetotail.
It was'not realistic, however, with this
type of instrumentation, to try to meas-
ure electrons in excess of about 1 MeV
in the plasma sheet. The instrument was
quite effective during solar particle
events for E.-Eg. Obviously, greater
geometry would have been desirable.
For example, it was only during the
April 1969 solar electron event (the
largest in the history of space measure-
ments) that Eg and E? provided useful
data.
Because of the wide variation in pro-
ton fluxes and energies encountered, it is
difficult to design a proton spectrometer
that works well throughout the magneto-
sphere. A serious count-rate problem
was encountered in measuring protons
mirroring near the equatorial regions in
the heart of the outer belt. The high
-8-
count rates in P. and P5 were enough to
cause partial paralysis of P_ and P3.
The paralysis produced minima near
90 deg in the pitch-angle distributions for
these channels. The paralysis was quite
consistent. It was only with some reluc-
tance, following studies with Flight
Unit 2, that we had to abandon the result.
The experiment provided good meas-
urements in most of the outer magneto -
sphere. Results in the magnetotail were
confined to P-, and P2< and P,. During
solar particle events, P..-P,. were effec-
tive, with occasional significant results
in Pfi and P?. Alpha channel a. provided
good data during solar particle events.
However, due to a pulse-pileup problem,
a, results were of no value for L £ 4, at
least in the region of appreciable trapped
proton populations.
MAGNETIC SHIELDING
The magnetic field of the larger elec-
tron spectrometer magnet between pole
pieces was about 2700 G; the field of the
smaller spectrometer magnet was about
860 G. The magnets were so mounted
that their external dipoles partially can-
celled. Because the cancellation did not
reduce the stray field adequately, we
installed additional shielding: a singleJ;
sheet of 4-mil Conetic about 1/2 in.
from the spectrometers. The Conetic
had to be annealed carefully before
^Conetic is a trade name, product ofthe Magnetic Shield Division, PerfectionMica Company. Reference to a companyor product name does not imply approvalor recommendation of the product by theUniversity of California or the U. S.Atomic Energy Commission to the exclu-sion of others that may be suitable.
assembly and not "work hardened" after-
wards. The package "depermed" to a
residual field of about 12 7 at 1 ft, which
was quite acceptable for the mission.
PITCH-ANGLE SCANMECHANISM
Because OGO-5 was oriented with
respect to the earth and the sun, the
aperture of the experiment had to be
scanned relative to the spacecraft. The
OPEP's were scannable at 1.5 deg/sec as
a normal spacecraft function, but thiscapability generally could not be used
because OPEP-1 and -2 were tied to-
gether rigidly; all OPEP experiments
would have scanned as a consequence.
Hence a special mechanism had to be
provided on OPEP-2 for scanning our$$experiment. It operated almost contin-
uously during the 3-yr mission with no
evident sign of malfunction. On alternate
orbits inside 4 R^, the mechanism was
turned off so a companion experiment on
the same scan platform could look for-
ward in the plane of the orbit (the OPEP
"gyro mode"). This reduced our inner-
belt data coverage by half.
We encountered a serious problem
with respect to the spacecraft scan mech-
anism. The requirement that our exper-
iment viewing-direction be tied into the
coordinate system of the vector magne-
tometer to ±1 deg did not seem to be fully
understood by the spacecraft people. The
spacecraft system determined the shaft
**This mechanism was supplied throughthe efforts of R. Browning, and laterH. Burdick, of the NASA-Goddard SpaceFlight Center.
-9-
PIN i
QlJN559
Q2ZH930 ZN559
Q5 Q6Its JI9I+ ZN325I
PtM*V OUTPUT
1. M.L TRANilbTORS. PEKLES 116-va
2. * • DENOTti MtTALPER MIL ^PtC f OR, RN'b'iCOR
Fig. 6. Differential discriminator. This LLL circuit design is capable of zerostandby power and wide operating temperature; it is fast and cannot be trickedby overload pulses, even those lasting tens of microseconds.
ANTI -COINCIDENCE -
PITA 14 ciwo
Fig. 7. Typical proton logic circuit. The anticoincidence portion of the circuit(CR1, Q3, Rg, R^, R^, Rg, R-j) is identical in principle to that used inthe discriminator (Fig. 6).
-10-
angle through the use of seisin angle re-
solvers. This system, capable of frac-
tional degree accuracy, was calibrated at
best to 5 deg. Thus, we had to effect an
inflight calibration using trapped particle
fluxes in predictable regions. Part of
this calibration effort is still going on.
DIFFERENTIAL DISCRIMINATORAND PROTON LOGIC
A circuit designed at LLL prior to the
start of the OGO-5 work proved invalu-
able in implementing our experiment
design. Figures 6 and 7 show its use.
The circuit uses zero standby power, is
fast, and cannot be tricked by overload
pulses. Although it has been reported
(McQuaid. 1966; West et al., 1969). it
does not seem to be widely used.
A differential discriminator (Fig. 6),
which is easily expandable to multichan-
nel use, was employed in the electron
system. Negative pulses are supplied to
integral discriminators 1 (CR1.Q1) and 2
(CR2, Q2). Tripping discriminator 1
results in anticoincidence of the differ-
entiated pulse from discriminator 2 (the
output comes in the trailing edge of the
pulse from discriminator 2); this occurs
through the tripping of tunnel diode CR3,
which in turn saturates transistor Q3.
Note that once CR3 is tripped, via cur-
rent through R6 and R7, it stays in con-
duction until discriminator 2 is turned off
(the current through R7 is sufficient to
maintain the tripped condition). Thus,
long saturating pulses at the input cannot
produce an output. Also note that Q3 is
in hard conduction when CR3 is on; this
means a delay of ~0.7 /usec before Q3
comes out of conduction, so that the anti-
coincidence function is maintained for
this period. The tunnel diode and tran-
sistor are temperature-compensating,
ensuring that the delay is constant over a
wide temperature range.
Figure 7 shows a similar system used
in the proton logic. Ql, Q2, and Q6 form
a standard series-coincident circuit.
CR1 and Q3 form the anticoincidence
logic, which operates as previously dis-
cussed. In this case, current through R9
plus current from either R4, R5, R6, or
R7 results in anticoincidence.
EXPERIMENT STATUSAND FAILURES
A large amount of housekeeping data
were brought out of the experiment in
order to keep track of its status. Once
every orbit, near apogee, an inflight
pulse generator was exercised to check
out the system. This test always gave
positive results, an important factor in
establishing the credibility of the data.
Some partial failures were observed.
In August 1968, we discovered that noise
associated with the Goddard Space Flight
Center (GSFC) scan mechanism was get-
ting into the bottom channels of the proton
telescope. The problem was most pro-
nounced in P« and usually could be local-
ized to a small range of scan angles.
For the first few weeks of OGO-5's
operation, we encountered occasional
problems in the electronically associated
channels E_, EB?, O., and O™. Noise,
seldom lasting more than 10 min at a
time, was being generated, probably as
a result of bulk or surface leakage in
either the E? or EB_ detector. After
the first few weeks, this noise disap-
peared and was never a problem
afterwards.
-11-
In the Spring of 1971, a detector prob-
lem appeared in the associated channels
E,, and EB« (the two detectors were mul-b otiplexed into the same preamplifier). The
channels became noisy. However, Eg
responded to outer belt fluxes and, based
on the resulting spectrum, appeared to
give correct results. We found that just
prior to this time, OGO-Operations had
turned off the experiment; in restoring it,
personnel had failed to turn on the experi-
ment's high voltage. After the high volt-
age had been on for a few weeks, the
noise disappeared. We cite this as the
kind of solid-state detector failure that
can occur after prolonged operation in a
space environment (3 yr).
RAW DATA PLOTS
We used two plotting schemes for rou-
tine examinations of our data: a 20-min
plot and a 2-hr plot. Many of these, for
1963 and 1969, are available at the
National Space Science Data Center.
Figure 8 is a 20-min plot of E, data*)
obtained at the heart of the inner belt.
The I's are the electron data (4.6-sec
averages) and the O's are backgrounds
(4.6-sec averages, counted only one-
quarter of the time). The zig-zag pat-
tern gives the magnetic aspect angle,
which is read from the scale at the upper
right of the plot. The normalization of
the background to the electron data is
1.01 ± 0.02. The electron-to-background
ratios in the inner belt for the lower en-
ergy channels (Ej-E.) are considerably
better than for the E- data. Figure 9
shows P0 data obtained the same time as£
the E,- data; the background normalization
is 1.0.
Figure 10 shows E- data in a 2-hr plot
overlapping the time period of Fig. 8.
The electron data are 4.6-sec averages,
and the background data are 73.7-sec
averages. Because of the long averages
for the background, some of the back-
ground structure has been averaged out.
The scatter of points in the electron data
is due, of course, to the scan modulation
of the data.
Figure 11 shows P? data in a 2-hr plot
covering the same period as the E- data.
Note that saturation effects are occurring
for the period 1724 to 1820 UT.
-12-
OGO V DETECTOR ORBIT YEAR MONTH DAY YDAY LSAV HOUR HIM. SEC. RUN REEL FiLE RECORD KBIT i-C- R£: ?X, SEC ritUlT. E5 3 58 HAR 9 09 5 19 3 8.9 50 2 6 1 IPS 3 3FitiAL EB5 19 22 47.4 8 2 15
__ _ _<Sfc»5 .8.
1912
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201.410.2
1918
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9.83201.3
27.7211.7
14.0
1920
2.0782.12210.952S3.5
29.9214.6
15. C
«GSE«GSH«5SK
Fig. 8. £5 inner-belt data in a 20-min plot. The flags are electron data and the O'sbackground. The background normalization is close to 1.00. These data aretypical of the EI - E5 data in the inner belt where background due to highenergy penetrating protons is a potential problem. The coordinates along theabscissa are: universal time, R in RE, L in RJT, ^m (magnetic latitude),
(solar ecliptic azimuth), 0QSE (elevation above the ecliptic plane),(s°lar magnetospheric azimuth), and 0GSM (s°lar magnetospheric
elevation).
-13-
OGO V DETECTOS 3R8IT YEAR MONTH DAY Yt'AY LDAY HOUR H!N. SEC. RUN REEL TILE RECORD KBIT i-0 RiC YJ.', ?l'. *iINI7. P2 3 68 HAR 9 65 5 19 3 8.9 50 2 6 ! !P8 3 3FINAL P82 is 22 47.4 a 2 :s
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1910
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197.28.5
1912
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1914
1.7901.7707.13
196.422.5
205.111.7
1916
1.8861.8868.56
198.925.2
208.612.9
1918
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1920
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Fig. 9. ?2 inner-belt data in a 20-min plot,to 1.00.
The background normalization is close
-14-
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02954325.356.47.45.6
Fig. 10. data in a 2-hr plot.
-15-
OGO VINIT.
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8 19 19 19 19 19 20 20i 0 12 24 56 48 0 12082 1.194 1.695 2.270 2.851 5.564 5.869 22.D54654 1.184 1.657 2.560 5.061 5.724 4.545 25.525.85 -10.05 5.49 12.82 16.44 18.40 19.50 IEi.554.8 171.6 195.7 207.7 218.2 226.7 255.8 526.41.2 -10.1 19.4 55.6 41.2 45.6 48.5 37.4S.8 167.7 201.4 219.7 251.2 259.2 245.2 515.6(.5 -4.8 10.2 16.5 19.2 20.5 21.1 16.6
Fig. 11. in a 2-hr plot.
-16-
Bibliography of Results
REPORTS
The LRL Electron and Proton Spectrometer on NASA'sOrbiting Geophysical Observatory V(E) '
(Instrumentation and Calibration)
H. I. West, Jr., J. H. Wujek, J. H. McQuaid, N. C. Jenson,R. G. D'Arcy, Jr., R. W. Hill, and R. M. Bogdanowicz
Lawrence Livermore Laboratory, University of CaliforniaLivermore, California
Lawrence Livermore Laboratory Report UCRL-50572, June 1969
The design, construction, and calibration of the LLL electron arid proton experi-
ment on the OGO-V satellite are described. A brief account of postlaunch results is
included. The electron spectrometer consists of two small permanent magnets used
for energy analysis with electron detection provided by solid-state detectors. Back-
ground detectors are also provided. The energy range covered is approximately 60 to
2950 keV in 7 differential energy channels. Geometrical factors vary from 0.18 to
8.6 cm2-keV-sr.
The proton spectrometer consists of a single solid-state detector and a range
energy telescope of four solid-state detectors situated in line with the entrance aper-
ture of the larger of the electron spectrometer magnets. The energy range is 0.1 to
94 MeV in 7 differential energy channels. The geometrical factor for the lowest energy-3 2
channel (0.1 to 0.15 MeV) is 2.06 X 10 cm -sr and for the rest of the proton channels_2 2
1.3 to 1.9 X 10 cm -sr. Data handling in the experiment is primarily digital using a
binary floating-point compressional scheme. The experiment apertures are scanned
relative to the stabilized spacecraft for obtaining pitch-angle distributions.
The LLL Electron and Proton Spectrometer on NASA'sOrbiting Geophysical Observatory V
(The data user's guide to the microfilm records)
H. I. West, Jr.
Lawrence Livermore Laboratory, University of CaliforniaLivermore, California
Lawrence Livermore Laboratory Report UCRL-51037, June 1972
This report provides background for using data from the LLL energetic-particle
experiment conducted on OGO-5. These data have been plotted on both 20-min and 2-hr
We give the abstracts of reports here because this information is not as readilyobtainable as the talks and publications that follow. Also, the latter information issummarized in the resume of results.
-17-
scales. Data from the UCLA magnetometer experiment have been plotted to the 20-min
scale for correlative purposes. In addition, tables of pertinent attitude-orbit data have
been plotted. Many of these data are available on microfilm from the National Space
Science Data Center.
The LLL Electron and Proton Spectrometer on NASA'sOrbiting Geophysical Observatory V(E):
The Three-Way Merged Tape(An Archival Data Base)
M. M. Zeligman and J. R. Walton
Lawrence Livermore Laboratory, University of CaliforniaLivermore, California
Lawrence Livermore Laboratory Report UCRL-51314, November 1972
This is a description of a data base that can be used for archival records. The
data are combined from three sources and thus the name of the resultant tape: The
Three-Way Merged Tape.
The data contained on these tapes came from the following sources:
The LLL Electron and Proton Spectrometer (Experiment E-06)on NASA's Orbiting Geophysical Observatory V(E).
Attitude-orbit tapes containing the satellite ephermeris providedby Goddard Space Flight Center.
Magnetometer tapes provided by Drs. Paul J. Coleman andC. T. Russell with data from the Triaxial Fluxgate MagnetometerExperiment (Experiment E-14) on OGO-5.
TALKS
Observations of Energetic Electrons and Protons on OGO-V
Harry I. West, Jr., Raymond G. D'Arcy, Richard W. Hill,John R. Walton, and G. Allen McGregor
Lawrence Livermore Laboratory, University of CaliforniaLivermore, California
International Symposium on the Physics of the MagnetosphereWashington, D. C., September 3-13, 1968
-18-
Electron and Proton Pitch Angle Distributionsin the Outer Magnetosphere
Harry I. West, Jr., Richard W. Hill, John R. Walton,and Richard M. Buck
Lawrence Livermore Laboratory, University of CaliforniaLivermore, California
Raymond G. D'Arcy, Jr.
Bartol Research Foundation, Franklin InstituteSwarthmore, Pennsylvania
EOS Trans., Amer. Geophys. Union 50, 659, 1969
Observations of Magnetopause Crossings by OGO-5
K. W. Ogilvie and J. D. Scudder
NASA-Goddard Space Flight CenterGreenbelt, Maryland
H. I. West
Lawrence Livermore Laboratory, University of CaliforniaLivermore, California
EOS Trans., Amer. Geophys. Union 50_, 661, 1969
Anisotrppic Angular Distribution of Protons and Electronsfrom the Cosmic Ray Solar Flare of November 18, 1968~
Raymond G. D'Arcy
Bartol Research Foundation, Franklin InstituteSwarthmore, Pennsylvania
Harry I. West, Jr.
Lawrence Livermore Laboratory, University of CaliforniaLivermore, California
EOS Trans. Amer. Geophys. Union j31_, 410, 1970
Simultaneous Measurementsof Solar Flare Electron Spectra in Interplanetary Space
and Within the Earth's Magnetosphere
Harry I. West, Jr.
Lawrence Livermore Laboratory, University of CaliforniaLivermore, California
A. L. Vampola
Space Physics Laboratory, The Aerospace CorporationEl Segundo, California
EOS Trans., Amer. Geophys. Union 5^, 411, 1970
-19-
Electron Spectra in the Slot and the Outer Radiation Belt
H. I. West, Jr., R. M. Buck, and J. R. Walton
Lawrence Livermore Laboratory, University of CaliforniaLivermore, California
EOS Trans., Amer. Geophys. Union 5L, 806, 1970
Evidence for Thinning of the Plasma Sheet During' the August 15, 1968 Substorm
R. M. Buck and H. I. West, Jr.
Lawrence Livermore Laboratory, University of CaliforniaLivermore, California
R. G. D'Arcy, Jr.
Bartol Research Foundation, Franklin InstituteSwarthmore, Pennsylvania
EOS Trans., Amer. Geophys. Union 51. 810, 1970
' • .OGO-5 Observationsof Substorm-Associated Energetic Electrons
on 15 August 1968
Margaret G. Kivelson and Thomas A. Farley
Institute of Geophysics and Planetary Physics, University of CaliforniaLos Angeles, California
Harry I. West, Jr.
'e Laboratory, Univvermore, Californi
EOS Trans., Amer. Geophys. Union 51, 810, 1970
Lawrence Livermore Laboratory, University of CaliforniaLivermore, California
The Butterfly Pitch Angle Distributionof Electrons in the Postnoon to Midnight Region
ofthe Outer Magnetosphere as Observed on OGO-5
H. I. West, Jr., R. M. Buck, and J. R. Walton
Lawrence Livermore Laboratory, University of CaliforniaLivermore, California
EOS Trans. , Amer. Geophys. Union 53, 486, 1972
-20-
Energetic Protons as Probesof Magnetospheric Particle Gradients
R. M. Buck and H. I. West, Jr.
Lawrence Livermore Laboratory, University of CaliforniaLivermore, .California
R. G. D'Arcy
Bartol Research Foundation, Franklin InstituteSwarthmore, Pennsylvania
EOS Trans., Amer. Geophys. Union 53, 486, 1972
Energetic Particles Near the Noon Magnetopausea s Observed o n O G Q - 5 ~
R. M. Buck and H. I. West, Jr.
Lawrence Livermore Laboratory, University of CaliforniaLivermore, California
American Geophysical Union meetingWashington, D. C., Spring 1973
Inner Belt Electrons in 1968 Observed on OGO-5
H. I. West, Jr. and R. M. Buck
Lawrence Livermore Laboratory, University of CaliforniaLivermore, California
American Geophysical Union meetingWashington, D. C., Spring 1973
A Unified View of Electron Pitch-Angle Distributionsin the Equatorial Regions'
of the Outer Magnetosphere—OGO-5 Observations
H. I. West, Jr.
Lawrence Livermore Laboratory, University of CaliforniaLivermore, California
Invited paper, American Geophysical Union meetingWashington, B.C., Spring 1973
-21-
PUBLICATIONS
Simultaneous Observations of Solar-Flare Electron Spectrain Interplanetary Space and Within Earth's Magnetosphere
H. I. West, Jr.
Lawrence Livermore Laboratory, University of CaliforniaLivermore, California
A. L. Vampola
Space Physics Laboratory, The Aerospace CorporationLos Angeles, California
Phys. Rev. Lett. 26, 458, 1971
Energetic Electrons and Protons Observedon OGO-5, March 6-10, TWTS
H. I. West, Jr., J. R. Walton, and R. M. Buck
Lawrence Livermore Laboratory, University of CaliforniaLivermore, California
R. G. D'Arcy, Jr.
Bartol Research Foundation, Franklin InstituteSwarthmore, Pennsylvania
Solar Geophys. Data ESSA Report UAG-12, 124, 1971
Shadowing of Electron Azimuthal-Drift MotionsJear theNoon Magnetopause
H. I. West, Jr., R. M. Buck, and J. R. Walton
Lawrence Livermore Laboratory, University of CaliforniaLivermore, California
Nature Phys. Sci. 240. 6, 1972
Energetic Electron and Proton Solar Particle Observationson OGQ-5, January 24-30, J97T~
H. I. West, Jr., R. M. Buck, and J. R. Walton
Lawrence Livermore Laboratory, University of CaliforniaLivermore, California
R. G. D'Arcy, Jr.
Bartol Research Foundation, Franklin InstituteSwarthmore, Pennsylvania
Solar Geophys. Data ESSA UAG Report UAG-24, Part 1, 113, 1972
-22-
Electron Pitch-Angle DistributionsThroughout the Magnetosphere as Observed on OGO-5
H. I. West, Jr., R. M. Buck, and J. R. Walton
.vermore Laboratory, University iLivermore, California
J. Geophys. Res. 78, 1064, 1973
Lawrence Livermore Laboratory, University of CaliforniaLivermore, California
Satellite Studies of Magnetospheric Substorms on August 15, 19687. OGO-5 Energetic Proton Observations — Spatial Boundaries
R. M. Buck and H. I. West, Jr.
Lawrence Livermore Laboratory, University of CaliforniaLivermore, California
R. G. D'Arcy, Jr.
Bartol Research Foundation, Franklin InstituteSwarthmore, Pennsylvania
J. Geophys. Res. 78, 3103, 1973
Satellite Studies of Magnetospheric Substorms on August 15, 19686. OGO-5 Energetic Electron Observations —
Pitch-Angle Distributions in the Nighttime Magnetosphere
H. I. West, Jr., R. M. Buck, and J. R. Walton
Lawrence Livermore Laboratory, University of CaliforniaLivermore, California
J. Geophys. Res. 78, 3093, 1973
-23-
Resume of Results
Initially, the perigee of OGO-5 was
291 km and apogee was ~24 R,-,. TheHiorbit inclination was 31 deg at launch
(March 1968), increasing slowly to
54 deg in 1971. The orbital period was
~2-l/2 days. The experiment obtained
useful data throughout the orbit. During
most of 1968 and part of 1969, OGO-5
made many inbound passes during which
it stayed close to the geomagnetic equa-
tor from about 15 R_ into 4 R,-,. This,is ±LJcoupled with the fact that OGO-5 pro-
vided about 95 percent data coverage
during the mission, meant that we were
able to do an extraordinarily good job of
acquiring data in the equatorial regions
of the magnetosphere.
During most of the time that the pitch-
angle scan mechanism was in operation,
our experiment scanned so as to look out
perpendicular to the earth's radius (the
choice was dictated by the operational
makeup of the spacecraft). Consequently,
our angular coverage in much of the mag-
netosphere varied from 90 deg to the dip
angle of the local magnetic field. Equa-
torial coverage thus meant complete
pitch-angle coverage and, of course,
equatorial pitch-angle measurements
also meant a complete knowledge of what
was going on along the field lines. Away
from the equator, in a dipole-like field,
the coverage was largely limited to pitch
angles near 90 deg. Near the noon mag-
netopause, however, the field configura-
tion is close to being circular and here,
even at high latitudes (45 deg geomag-
netic), good pitch-angle coverage was
available. Conversely, in the magneto-
tail during substorm growth phases, the
magnetic field approached the radial
direction. During these times, the pitch-
angle coverage could be as limited as
90 ± 20 deg. When needed, complemen-
tary electron data from the UCLA scintil-
lation counter experiment were available.^
As will be seen later, the limited pitch-
angle coverage in the magnetotail had its
compensations; it was ideal for using the
proton east-west effect in the study of the
plasma sheet boundary during substorms.
The experimental results are dis-
cussed below in terms of the inner belt,
the slot and near-by outer belt, pitch-
angle results in the outer magnetosphere,
plasma sheet boundary during substorms,
and solar particles. Some of this work
is published or in publication, while the
rest is in process of completion.
INNER BELT
Data were studied in the inner belt
region for those orbits during which the
experiment scanned. The values of j. at
discrete L-shell crossings were obtained
and were plotted in terms of j. vs X ,
(here, X , is the magnetic latitude as
determined from the dipole equations
B/B Q = (I/cos 6X d ) (4-3 cos2Xd)1 /2 .
Figure 12 shows an example of the
ordering of the data. To a good order of•j, -j*
approximation, we and others (e.g.,
Pfitzer et al., 1966) find that the shape of
This experiment, conducted byT. Farley and M. Kivelson, consisted ofsix scintillation counters looking in differ-ent directions.
* *_This is a reasonable approximation
well away from the loss cone.
-24-
£•078e
E»0888
E»OS88
E«0388
E«0286
£•01
Q.CCLJa
CALC. LAMBDA M L= 2.00RUN 3/27 LINEAR LAMBDA TIME FIT DAYS 69-293
Fig. 12. EI j±-fluxes for L = 2 in 1968 plotted as a function of Xd. Note that the Xdused here is derived from the dipole equation. These low-energy electronsshowed little decay during 1968 whereas the higher energies showedappreciable changes (especially E$ and £5).
the distribution (j -vs-X , being equivalent
to jj-vs-equatorial-pitch-angle) is inde-
pendent of energy. This finding has
allowed us to order the data in terms of
equatorial j, - values.
L-plots of equatorial fluxes for 1968
and early 1969 are shown in Fig. 13. The
curves starting at L = 1.3 indicate the
flux in early 1968. All energies except
E, decayed slowly until the large inner-
belt injection during the October 31-
November 1, 1968, magnetic storms.
The poststorm radiation belt rearrange-
ment effects also are indicated in Fig. 13;
-25-
10'
u0)
<U
-*I
U
O
O0)
10'
CO
0>
I 10C
H 10in
10
. , I
288,293,303
288,293,303
288,293,303 -4
288,293,303 -
1.0 1.5 2.0
L-shell
2.5 3.0
Fig. 13. Equatorial j^-values for 1968 plotted as a function of L.Major inner-belt injection occurred on Days 305 and306. The various curves show the rearrangementeffects that occurred following injection.
unfortunately, the perigee crossing was
at L = 1.8 on November 1, so that deep
inner-belt coverage was not possible.
It is surprising how stable the E^
fluxes are. They did not rise appreciably
during the major injection even though the
fluxes of the next higher energy channel
(£„) rose above those in Ej. Conversely,
we are fascinated by the relatively rapid
changes in E. and E&. We believe the
data in Eg (Fig. 13) to be a Starfish resid-
ual. The E? fluxes were of comparable
-26-
10J
CN
u0)
0_yi
o
•5 10'
West (STARAD)
Pfitzer(OGO-l)
-Pfitzer :OGO-3)
West (OGO-5)
• L = 1.4 equatorial flux, 1 , 1 , 1 , 1 , 1
1962 1964 1966Year
1968
Fig. 14. Long-term decay of 2-MeVelectrons at L = 1.4. All datapoints were determined bymagnetic electron spectrom-eters. The data sources areindicated on the figure.
level but are not plotted in Fig. 13 due to
the greater difficulty in extracting these
data.
With our 1968 data, we combined
earlier data obtained in 1962 by West
(1965), in 1964 by Pfitzer (1968) andPfitzer et al. (1968), and in 1966 and
1967 by Vampola (private communication).
An energy of 2 MeV, which seems well
above the electron energies involved in
the usual inner belt dynamics, is chosen
for the L = 1.4 data plotted in Fig. 14.
The e-fold decay rate is ~370 days. Star-
fish electrons are no longer important in
radiation belt dynamics.
Electron spectra typical of the mid-
latitude regions are shown in Fig. 15 for
the period before the major injection
event. The data are normalized to point
out the spectral hardening as we approach
the earth. The spectrum changed greatly
as a result of the October-Novemberinjection.
SLOT AND NEARBYOUTER BELT
In the inner belt, the pitch-angle dis-
tributions are largely independent ofenergy. In the outer belt, by contrast,we find a marked energy dependence. A
good example of data we acquired is pre-
sented in Lyons et al. (1972), their Fig. 6;
these authors used our data as a point-in-
proof of their electron pitch-angle diffu-
sion theory. The pitch-angle data, along
10'
JH8
_Q
O
I 3_ 103
102
10'
NormalizedequatorialspectraDays 69 - 1841968
10' 102 103 104
Energy — keV
Fig. 15. Typical inner-belt electronspectra in the period March 4to October 31, 1968. Thespectra are normalized tofacilitate comparison. Major .changes occurred in the spectrafollowing injection onOctober 31-November 1.
-27-
with the theoretical comparisons, are
shown in Fig. 16. Other examples are
shown in Fig. 17. Salient features of
these results are the flat pitch-angle dis-
tributions prevailing at the higher ener-
gies and the appearance of what may be
described as a bell-shaped distribution
sitting on a broader flat distribution for
the lower energy electrons. At present,
it has not been established whether these
features are time-independent; possibly
some of them evolve during storm time
injection and are modified later. The
resolution of this point is the subject of
further investigation. Unfortunately, the
OGO-5 equatorial data coverage in this
region is not as complete as we would
like.
We have carried out a study of storm-
time injection and decay. The data were
obtained during a relatively mild storm
(peak DST = -94y ) on June 11, 1968.
Preliminary results were presented by
West et al. (1970). Pitch-angle correc-
tions based on studies described in the
previous paragraph still need to be made;
hence, we still consider the results
preliminary.
Plots of j .-vs-L provide part of the
picture. Figures 18 and 19 show data
from Day 158, 1968, obtained three days
before the storm. Figure 20 presents
storm-time data for Day 163. Figure 21
shows data on Day 176, 13 days after the
storm. At this time, the outer belt is
believed to have been in diffusive equi-
librium.
Taking j, from such plots as Figs. 18
through 21, we have prepared the time
plots shown in Figs. 22 and 23 for L = 3.5
and L = 4.5. No pitch-angle cor-
rections have been made; this may
account for some of the scatter in the
data. Features to be specially noted are
90 1800 90Equatorial pitch angle — deg
Fig. 16. Electron equatorial pitch-angle distributions obtained April 25, 1968, com-pared with theory (solid line). [After Lyons et al. (1972)]. Lyons et al.calculate a combination of cyclotron and Landau resonant diffusion cTrfven bythe average observed band of plasmaspheric whistler-mode radiation (hiss).There can be no doubt that they have pinpointed the major effects controllingthe energetic electron fluxes in this region of space.
-28-
March 30, 1968
10L=3.89
>GSM~356°
X =-1.0m
E 4 ~10. & E . < 10°5 o
60 90 0 30 . 60 90
Fig. 17. Electron pitch-single distributions obtained March 30, 1968. This is anotherexample of slot-region pitch-angle data similar to that shown in Fig. 16.For perspective, note the corresponding radial profile data in Fig. 26.
the drop in the high energy fluxes during
storm time and the rise of the low-energy
fluxes; the relatively rapid decay of E0,ft
E«, and E .; and the growth of E,., Ec, and*3 4 • O D
£„ followed by slow decay. Obviously,
the decay rates are energy-dependent.
For shells ~3 to 4.5, the lower energy
channels E, - E. have e-fold decay rates
of 1.4 to 3 days. The decay rates for Ej.J
are 3 to 4 days, for Eg are 6 to 7 days,
and for E? are 10 to 14 days.
The electron spectrum can change
markedly as a function of time. Fig-
ures 24 and 25 show the post-recovery
diffusion effects for L = 3.5 and L =4.5.
The curves are annotated to show the
number of days after the storm. Fig-
ure 26 shows the changes in spectrum as
a function of L-shell for Day 181. Note
the evolution of a marked high-energy
peak in the slot region. This is charac-
teristic of the slot at weeks to months
after injection.
PITCH-ANGLE DISTRIBUTIONSIN THE OUTER MAGNETOSPHERE
We have had a major preoccupation
with these data; accounts of our efforts
are to be found in West et al. (1969) and
West et al. (1972 a,b,; 1973 a,b). We
-29-
10C
oo>
0)-XI
CMEo.
u<0
10"
10
I02
10
10
10-1
June 6, 1968Day 158
m19.6 30.0
26.0°
GSM
'GSM
35.0°
121.4
41.8°
5
38.0' 39.0 41.1'
135.1
48.7'
41.9' 42.. 2
Fig. 18. Outbound radial flux profile on Day 158, 1968. This quiet-timedata (also Fig. 19) sets the stage for the changes that occurredduring the storm on Day 163, 1968.
-30-
I • . IJune 6, 1968Day 158 .
\ -37.9° -45.5° -23.9° -15.9° -11.8° -9.3° -7.7 -6.8
GSM 280.6° . 263.8°
GSM -26.6° -8.1°
Fig. 19. Inbound radial flux profile on Day 158, 1968.
-31-
June 11, 1968Day 163
27.0
GSM
GSM
Fig. 20. Outbound radial flux profile on Day 163, 1968.
-32-
10"
o 10
r
ioEo
o£ 10'
_Q)
4)
10'
10-1
I ' IJune 24, 1968Day 176
m
2 3
11.0° 20.2
^GSM
GSM
4 5
24.2° 26.0°
107.7°
33.8°
26.9°
7
26.9°
130.2°
46.4°
8
26.4°
9
25.5°
Fig. 21. Outbound radial flux profile on Day 176, 1968. The electronsshould be in a state of diffusive equilibrium at this time.
-33-
10 15 20 25 30
-100
Fig. 22. TLme history of j,-fluxes on L-shell 3.5 before,during and after the June 11, 1968, magnetic storm(Day 163). These data are preliminary since pitch-angle corrections have not been made.
-34-
10-1
5 10 15 20 25 30 5 10 15
-100
Fig. 23. Time history of the j^-fluxes on L-shell 4.5 before,during, and after the June 11, 1968, magnetic storm(Day 163). These data are preliminary since pitch-angle corrections have not been made.
-35-
10C
10'
o4)
(I)
cp
u0>
IO5
10'
10'
Day UT
o!58 0419• 163 0847o 163 1018o!66 0040• 168 1525• 171 0540*173 1842A 176 1039o 179 0047
Xm
-32.7-10.222,836.822.031.6
-28.222.6.36.9
+ 3
+ 5
10° 10"
Energy — keV
Fig. 24. Changes in spectra at L-shell3.5 as a function of time afterthe June 11, 1968, storm. Thevarious spectra are labeled,to show number of days follow-ing the storm.
have studied the equatorial pitch-angle
distributions of electrons at all local
times throughout the magnetosphere. As
a result, we have acquired an overall
view we wish to present. We have also
10'
10'
r 10'
4)J*
CM
^ 10'V)
iu
4)
I 10*
10
10
Day UT* 163 0819« 163 1049a 165 2309* 171 0346* 176 1056° 181 1530
1 '""IX
IT)
-3.326.3
-29.9-17.925.425.8
+ 18
10' 10" 10° . 10*Energy — keV
Fig. 25. Changes in spectra at L-shell4.5 as a function of time afterthe June 11, 1968, storm. Thevarious spectra are labeled toshow number of days followingthe storm.
studied the proton pitch-angle distribu-
tions. These data are more subjective
than the electron results, not as well
understood, and, hence, discussed more
briefly.
-36-
We start in the prenoon magnetosphere.
The electron pitch-angle distributions in
this region are always normal. (Here we
are referring to distributions that are
symmetrical and peaked at 90 deg and
have a loss cone. They are often shaped
like the normal probability distribution
and are encountered all the way to the
magnetopause.) The radial profile of
jj-vs-L for March 30, 1968 (Fig. 27) pro-
vides perspective for presenting some
pitch-angle data. Figures 17, 28, and 29
show the pitch-angle results acquired.
These results are quite typical of this
region of the magnetosphere.
As electrons drift through the noon
magnetosphere at extended distances,
changes can occur as a result of drift-
shell splitting. Assuming adiabaticity,
we find that the equatorially mirroring
particles follow contours of constant B.
Constant-B contours obtained by Fairfield
(1968) for an average magnetosphere are
shown in Fig. 30. Conversely, as shown
by Roederer (1967, 1969), particles with
small equatorial pitch-angles, drift so as
to keep the length of their bounce path
approximately constant, all-the-while
maintaining a constant mirror field. If,
for example, we examine data at 9 R_,Jtii
and 0900 local time and contrast themwith data at 9 R^ and 1500 local time, wetiimight expect to find changes in electron
fluxes having pitch-angles near 90 deg.
An effect indeed occurs, as exemplified;
by the radial profile data in Fig. 31 and
the pitch-angle data in Fig. 32. We call
these pitch-angle distributions with min-
ima near 90 deg "butterfly" distributions.
We consistently find this effect of "mag-
netopause shadowing" in the equatorial
region beyond roughly the constant-B
10C
Q) "J
-* 10
Eo
o
10'
10i
: 4.5,-8.0-/
r-4.0,-10.8
June 29, 19681233-1414 UTDay 181
I I
10 10 10
Energy — keV
10"
Fig. 26. Changes in spectra as a functionof L-shell on June 29, 1968.
contour that maps from noon to about
7 RE at local midnight (see Fairfield's
data in Fig. 30).
Starting near dusk, as we go into the
nighttime magnetosphere, another aspect
of drift-shell splitting comes into play.
The appearance of a tail-like magnetic
field further contributes to the generation
of the butterfly distribution. This effect,
which we call "configuration-change
drift-shell splitting," is well known. By
contrast, the effect of magnetopause
-37-
o0)
o_*i
10"
iof
10
CM
iot/lcs
10*"
10-1
i r i i rMarch 30, 1968
1 79 kev
3 4 5 67 8 9 10 11 12
X -35.6° -0.3° 6.9° 10.2 11.2 10.3m -8.3° 4.0° 8.9° 10.9 10.9
GSM
VGSM
337°
-4.4°
322°
•10°
Fig. 27. Radial flux profile on March 30, 1968.
-38-
March 30, 1968
*GSM~330°
L = 8.38 X =10.5°
><u-*i
10C
105
It»_ooI 10*
10'
1 = 6.93 X =8.8° L=5.41 X =5.4°m m
. E7
I30 60 90 0 30 60 90 0 30 60 90
Pitch angle — deg
Fig. 28. Typical outer-belt pitch-angle distributions obtained on themorning side of the earth March 30, 1968.
<u-fCM
March 30, 1968
""GSM"3220
L=10.98 X =11.0° L=10.14 X =11.2° L = 9.18 X =11.0°m m m
10-1 _L30 60 90 0 30 60 90 0 30 60 90
Pitch angle —deg
Fig. 29. Typical pitch-angle distributions near the morning magneto-pause obtained March 30, 1968.
-39-
GM12 10 8 0 -2 -4 -6 -8 -10-12-14-16-18-20
Fig. 30. Contours of constant equatorial-B for an average magneto-sphere [after Fairfield (1968)] . Equatorially mirroring particlesdrift at constant-B as long as the first adiabatic invariant re-mains conserved.
shadowing is an original discovery of this
experiment.
An example of the effects we obtained
in a quiet magnetosphere is shown in
the radial profiles of Fig. 33 and the
corresponding pitch-angle distributions
in Fig. 34. Inside ~9 R~, we attribute
most of the butterfly distribution to
configuration-change drift-shell splitting;
beyond roughly 9 Rp,, the results are due
to the combined action of both shell-
splitting effects. As indicated earlier,
we might expect to find the crossover
point of these effects more in the range 7
to 8 Rp,. Although some other data are
more in agreement with this expectation,
there seems to be a discrepancy indicat-
ing an area of future work. Serlimitsos
(1966) and Haskell (1969) have also
observed the butterfly distribution deep
in the nighttime magnetosphere. They
attribute the distribution to configuration-
change drift-shell splitting only, over-
looking the effect of magnetopause
shadowing.
The almost complete dropout in the
perpendicular fluxes beyond 9 RF, .as
shown in Fig. 33, is quite typical of the
premidnight outer magnetosphere during
periods of magnetic quiet. During dis-
turbed periods, some disruption of the
butterfly distribution occurs. The filling
in of the perpendicular fluxes occurs
more readily for the lower energies; how-
ever, in general, it is electrons, showing
the deep dropout in j., which drift into the
substorm region. For our purposes, this
is ~2300 ± 2 local time. The transition to
-40-
10°E I
10°iv
o
1 101
10-1
in \ i rJanuary 7, 1969
J_1 L 2 3 4 5 6 7 8 9 1 0 1 1 1 2
A -8.2° -31.3° -19.1° -8.0° -0.3° 5.0C
m
"GSMIGSM
-30.1° -26.1° -13.0°. -3.9° 2.6°
67.1° 40.5°
-17.3° 13.7°
Fig. 31. Radial profile of electrons in the afternoonmagnetosphere obtained January 7, 1968.Note beyond 8.5 RJT that j± is no longer thedominate flux in pitch angle. The relativelylarge fluctuations in ji may be due to thefact that these electrons in their eastwardazimuthal drift were closer to the magneto-pause than were the peak fluxes (at ~50-degpitch angles).
a tail-like field in the regions near mid-
night can mean the demise of the butterfly
distribution. We attribute this change to
a transition from guiding-center motion
of the electrons to one in which they get
caught up in the field reversals of the
neutral sheet (Speiser, 1965, 1967, 1971).
It is expected that the electrons can alter-
nate between these two modes until they
either precipitate or drift out of the inter-
action region. Figures 35 and 36 show
data acquired during the famous substorm
of 0714 UT, August 15, 1968. (For the
pitch-angle data see West et al., 1973;
this was part of a nine-paper substorm
study.) Prior to the start of the substorm
growth phase, the field was close enough
to a dipole configuration to maintain the
butterfly distribution. As the substorm
developed, the higher-energy electrons
changed to isotropy, followed by the lower-
energy electrons on a time scale of a few
-41-
10
o .<u ln4V 10
« 10"
E o< ]°2
Mc
o 101
j>(U
" 10°
10
January 7, 1969
*GSM=40-7°
R = 9.87. X = -0.6°,5 m
R = 9.38X =-2.2°
m
R=8.98X =-3.6°
m
30 60 90 0 30 60 90 0 30 60
Equatorial pitch angle — deg
XGSM=8 '3
R = 8.01\ =-7.3°
m
90 0 30 60 9'J
Fig. 32. Pitch-angle distribution of electrons ppstnoon in the distant magnetosphereJanuary 7, 1968. These pitch-angle distributions were transformed to themagnetic equator under the assumption that the position of the dipole equatoris still meaningful this close to the magnetopause.
minutes, Substorm expansion occurred
at 0714 UT. With the resulting occur-
rence of a dipole-like magnetic field,
fresh electrons showing the butterfly dis-
tribution drifted in from dusk. Magnetic
and wave-particle effects disturbed the
distributions so that the undisturbed
butterfly distribution was not observed
until about 0740 UT, which is near the
end of the substorm recovery phase.
Another example of substorm effects
is shown in Fig. 37. Here we show data
obtained near midnight. The data have
been plotted to 4.6-sec averages and are
shown in time sequence without any selec-
tion of angle. The pitch angles of the
particles being detected are indicated by
the panel marked "scan." Of course, only
qualitative pitch-angle information can be
obtained from these plots. By virtue of
the experiment-satellite orientation, the
outer envelope of "scan" is equal to the
field inclination and its complement; when
the envelope is narrow, we have a tail-
like field and when wide, a dipole-like
field.
In the bottom four panels we show the
UCLA magnetometer data in geocentric
solar magnetospheric (GSM) coordinates.
Four well-defined substorms occurred on
this inbound pass; expansion onsets
occurred at 1700, 2012, 2255, and
0108 UT as the field direction began to
rotate to a more dipolar direction. The
-42-
September 18, 1968
60°
40°
20°
uc
-20°
105
usI
0)_*I 10W
£ 10'uV
10V
6Xm -4.5°
*GSM 170°
ZGSM -1.43
(B meas - B dipole)/B dipole
7
-1.0°
-20°
-40°
8 9
1.9° 4.1°
161°
-0.85
10
5.8°
155°
0.07
11
6.9°
12
7.4°
151°
1.21
Fig. 33. The radial flux profile for September 18, 1968. Thefluxes labeled ji, are in reality the peak fluxes in thebutterfly distribution at pitch angles of 20 to 40 deg.Beyond about 9.5 Rjr, the magnetic field becamesomewhat tail-like, so the physical constraints placedon the field of view of our spectrometer meant we couldnot view at much less than 25 deg. The lower energydistributions peaked at higher angles than the higherenergies, accounting for the more complete coveragein jii at low energies. The dashed curves indicate someextrapolation in the data. K = 0+.
-43-
September 18, 1968
R=9.03
10*
± 10V
0)
J 102
I*»uJi 10(!)
0.1
*GSM=158°
R=8.07
1 ' r I ' ^El
I
R = 7.01
X =-0.9° <t>m
=164
30 60 90 0 30 60 90 0
Pitch angle — deg
30 60 90
Fig. 34. Pitch-angle distributions obtained just before midnight September 18, 1968.These distributions inside roughly 9 Rjp are typical of the entire nighttimesector.
electron pitch-angle effects are made
evident by the degree of modulation. Iso-
tropy shows as no modulation except for
statistical scatter. When we observe
modulation in this region of the magneto-
sphere, it is always due to the butterfly
distribution. Following the 2012 UT sub-
storm, we note the onset of enhanced
modulation in E2 at ~2100 UT and in E.
at ~2110 UT. A new substorm growth
period began as the field started to
become more tail-like; at ~2210 UT, we
note the abrupt transition from the butter-
fly distribution to isotropy. Following
the onset of expansion of the 0108 UT sub-
storm, we note the emergence of the but-
terfly distribution in £„ at ~0124 UT and
in E1 at ~0200 UT. It will be noted that
the proton fluxes P. also reflect substorm
effects. The pitch-angle distributions of
the protons are generally isotropic and do
not show the reemergence of the butterfly
during expansion. The butterfly distribu-
tion, however, is usually found in the
nighttime magnetosphere at roughly 6 to
9 Rg. Modulation in the proton fluxes in
Fig. 37 is to be noted, but, as discussed
later, this is due to plasma sheet gra-
dient effects.
Even during a quiet period, electrons
cannot drift through the nighttime mag-
netosphere to dusk without a considerable
modification occurring in the butterfly
distributions. Figure 38 shows data
-44-
80
10
10-
406
10"uSI
r 10°>01
lio2
I
lio1
10-2 _J I I
0600 UT 0700
8I7
0800
Universal time and radial distance
Fig. 35. Perpendicular and parallel electron flux during the0714 UT substorm on August 15, 1968. The electronenergy channels Ej, Eg, and Eg are centered at 79,266, and 822 keV, respectively. The jn shown dottedprior to -0655 UT was obtained from the UCLAexperiment and tacked onto the LLL data. The errorbars are an estimate of the uncertainty in this pro-cedure. The flux, jn, is actually the peak flux in theangular range 135 t'o 150 deg with respect to B. Thetotal magnetic field in the top panel was obtained fromthe UCLA magnetometer experiment.
-45-
80
o
10
406
oVV)
I 'O3
I
<0
10
1 101
JB(1)
10-1
10-20600 UT 0700
I9 R r 8
0800
Universal time and radial distance
Fig. 36. Perpendicular and parallel electron flux during the. 0714 UT substorm on August 15, 1968. This is the
same as for Fig. 34 except the electron channels£2, E4, and Eg are 158, 479, and 1530 keV, re-spectively.
-46-
3
4
3
2
1
0,\
4
3
f 2
•o i
i «8. -i1 *\I $
^ 4
i0
4
3
2
1
0
-1+ OA°
Inc no
Dec Q°
-90° 50
B,-v 251 n
isn"
Scan 9QOI
n«
UT
REX
m
*GSMXGSM
— i r i . . . . } . . . . t . . . . i , . . . .
1 1 1 1 1 1
. . / I '!/&,.... „ : -.. rtkf tt illSS5^ J - ^Sfe x..vV,;.-^ :. ..-..— "7 ""~..' " - ••_--—-_': -^; ^7j; ; >p ._.^r — ',m!17Ii " ^-2 ' • . » • • • "j . 'r- '"-^ • **.*•"' .*. «"
i I I i
pl
^?*£t-j •'•..;.•:•.•.•:..>•'.• .•'.-.•' /..'•.•.V^Vf^^^.j-A *•>'.'•••' -.-. •'••..!• • :-..••'.•.— ••; • •••' .••'.- •.'>•'«.".''.'.>.>•.->.• .'A.-.:...' .•'.•).••' .vX'-". '
i i i i
P2 -
^^r -•'•"••" •'"-;•;••• ~ •^r~-----*~~-:* "i '• ;-' v '""•-'"'"••" ":"•!".''' " ' ' " ' /s"% V .'V .'.
~-J--.Jjryv^— k t~~'V*Av^v .±~^—*± -.- " -- _L
^-Dipole inclination
__,A.,4 i . _.^ .Au*. «*.^ . -...- !• - jf ' ••
^ _____ ^ ^^-^ ^-^__x-'^'txV — '
•*!f*r*~^ ^~ !"IV~^~T"~~. ~ — ~\~ v^~--~^ (
— htttti — i i].i.m.imi i --m— - — -ThhitinyitiitiiitmnmnrniiiiiiiiiiumnifrnnniviniTiTTiiiiiiiiiiiiiiiiiiBiiriiiiiiiiriTmmtijiiiiiininimiiiifivTmpiiiiiiininiiiniimiiiiigeigtiMuiiuiiuiiiauin:inrainniiiirain]niiiniMjimi.*j.iiiiiii.ii Jiiiijjii>EtiituiBjii!iai]iiiiijii!iiiiiiiiM»iuiiniu>tmujujij-tiTniimTOnTiinra-jiiiiiau'cuuiujMLunrivram'tmiiiiiiBjiiuijiiuJiijiiiMiimM 'niMiwiiiiii'uiu
|"|' p| I I I I I 1 1 11 I1" ' I 'ilHWl"!
1 I I I 11700 1800 1900 2000 2100 2200 2300 2400 0100 0200I I I I I I I
18 17 16 15 14 13 12 11 10 9 8•2.8° -3.1° -2.4° -1.3° -0.1° 1.0° 1.8° 2.3° 2.2° 1.6° 0.5°
180° 190°23.0° 13.9°
Fig. 37. Scatter plot of data acquired during an inbound pass near midnight August 9,1968. The small dots show the data at 4.6-sec averages obtained at all pitchangles reached by the experiment scan, whereas the large dots indicate thebackgrounds. The panel labeled "scan" shows the range of pitch angles ob-served by the experiment; the outer envelope is equivalent to the field in-clination and its complement. The data show four well-defined substorms.
-47-
Os:
I
coU
4
3210
-1
5
43
1
0-1
..,,;..;.,.,-^:A^:^ .. ,_.£.>
54
3211
01
1 1 1 1 1 P i i i i-
^-JSBW*""—
- -'-- w'|.n ^, ->->->
. • : • - . :a.>iVi .«'.""*'^Tv^yftgy; r^v^:. ^spp - . '' •>..- •' ,•• " ''•"'y/l''"" ,
Yooo
4321
0-1
1 i i i i i i 1 ' ' 1 1
-_ ,.fj^SS.p ...^tf-gSs**
1 .,, ;0$^j( .;;.;:;-;. .:.;v-,-/i
;
•..•..:<^ f!H{.3$<!i®*&'*l*i'*'"t"*'"*~
.jf*^^^ fj.'*r
-..•:.. . , .-. •.ri-i-^Vx:ia^*-v£^iir:th;rf' . : ''"''"~I7'' ••.•a'.'J.' J. .- ''. V'-. ^" ' • '•'•V/'v'~'.":vrj:;; •_'."•'•'• '.'• '.' r.'"' •'• •"..''.•: .V '"'-•-' "''AV .'•'".'_'••''••'•'•' f'1 .'•'..'".•.' , ,
180°V
§ 90'1/1
0°vraniiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiHiiiiiiiiiiiiiMiiiiuiiiiiiiiiiiiiiiiiiiiiiii'iiiiiniiuiiiiiiiiiiiiiiiiiimiiiiiiiiiiiiuiiiiiiiiuiiiiiiiiiiiiiliiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiniiintiif'
250
250
250
50250
UT
m
18001
17
19001
16
3.4°
2000I
15
-2.1°
2100I
14
2200I
13
-4.6°
2300 24001
12I
11
-5.7°
110
010019
02001 1 18 7 6
0300
-6.9° -8.9"
GSMLGSM
I250°
14.0°
I255°0.4°
Fig. 38. Scatter plot of data during an early morning inbound pass whilein the plasma sheet June 5, 1968. See Fig. 37 for an explana-tion of the plots. The electron data are annotated to show thecharacter of the pitch-angle distributions evident in the variousregions.
-48-
acquired in the plasma sheet on an in-
bound pass at -0500 local time, during
which K was 2 . Figures 39 and 40
show the corresponding pitch-angle dis-
tributions. Note that as we approach
dawn, the change in the field configurar
tion leads to the demise of the butterfly
distribution inside radial distances of
about 9 Rp. Beyond this distance, the
loss of the butterfly distribution is due to
the disruptive influence of tail-like mag-
netic fields and plasma sheet noise.
Figure 41 provides a resum6 of the pitch-
angle results.
We believe this resume of our pitch-
angle results provides the proper overall
view of the effects occurring to the elec-
o0)
icr
o/
O
oV
-H 10'
1 ' I 'June 5, 1968Electron channel E
2209 UT
1938 UT
1758 UT
2026-2052 UT
I
1803 UT
30 60
Pitch angle — deg
90
Fig. 39. Pitch-angle distributions forEj at various times during theinbound pass June 5, 1968.
trons as they drift eastward around the
earth. The story is not complete, how-
ever. An area of major interest is the
noontime magnetopause (noon plus or
minus a few hours and plus or minus
about 50 deg in magnetic latitude). Here
there are questions about the mechanisms
that produce the magnetopause shadowing
effects we observe from a. few hours past
noon extending into the nighttime magneto-
sphere. It may be that the near
equatorially-mirroring particles leave
the magnetosphere directly at the mag-
netopause. Or it may be that they are
scattered by wave activity near the mag- .
netopause so as either to enhance the
fluxes at small pitch angles or cause them
to leave the trapping regions. There is
the possibility also that the equatorial
drift paths for electrons, rather than
mapping to the magnetopause near noon,
may split north and south through regions
of minimum B (that is, through minima in
B along the field line which are not at the
equator) and then come back together an
hour or two past noon. The possibility of
this mechanism was suggested by
Shabansky (1971) and discussed by
Roederer (1969) in his presentation of
field models. Roederer pointed out that
these high-latitude regions have not been
shown to connect topologically to the rest
of the magnetosphere; however, we find
copious quantities of electrons mirroring
in what would appear to.be high-latitude
minimum-B regions, judging from the
experimental results of Sugiura et al.
(1971). The population of the regions is
associated with a general high-latitude
buildup of fluxes near the magnetopause
for both electrons and protons. Our guess
is that the action of the minimum-B paths
-49-
June 5, 1968
2215 UT 2302 UT
105
104
. oT
J[ 103
V
SJ
E 90 1Q*
""x.«/)
iU |
•1 'o1
1
" 10°
in"1
R = 1 2 . 5 8 11.66X =-4.9 -5.4°m
i i | . i | , i i.
f 2302 UTC1
s^ *>r^-— . -^^^^ 2215 UT
E2 ^
s- -^
' ^^X^m
1 , 1 , . ! . .
2345 UTR= 10.75\ = -5.8°
T
, o 2357 UT' R=10.49
X = -5.9°m"1—T
i i I I i
0 30 60 90 0 30 30 90 0 30 60 90
Pitch angle — deg
Fig. 40. Pitch-angle distributions for E^, £3, and £3 at various times during theinbound pass June 5, 1968.
is important in determining the particle
motions.
Proton data may provide some insight
into the problem of azimuthal particle
drift by the noon magnetopause. One
would expect to find magnetopause shad-
owing effects in the prenoon magneto-
sphere. Although these effects are occa-
sionally found and become pronounced at
~0600 LT and earlier (that is, in the
nighttime magnetosphere), they do not
show in the same convincing way as for
electrons. For example, at 9 RF at
0900 LT, the typical pitch-angle distri-
bution is a narrow "normal" distribution
sitting on an isotropic background. We
have a very real problem in reconciling
the proton data to the clear effects of
magnetopause shadowing obtained for the
electrons.
PLASMA SHEET BOUNDARYMOTION DURING A SUBSTORM
The plasma sheet boundary motion was
was studied in detail during the 0714 UT,
August 15, 1968, substorm (Buck et al.,
1973). Figure42 shows the geometry
existing at the start of this substorm's
growth phase. The experiment scanned
looking out perpendicular to the earth's
radius vector, looking alternately from
west to east. It saw particles whose
-50-
YGSMEquatorial pitch angledistributions
15
15 --10 - V ~ /\
GSM
A Normal
f\f\ Butterfly
Isotropic
Fig. 41. . Survey of equatorial pitch-angle distributions throughout themagnetosphere. In those nighttime regions beyond ~9 Rgwhere a mixture of distributions prevail, the results arestatistical.
Plasma
IRe
0640 UT
Anticipated neutral
sheet position
GSM equator
Fig. 42. Scale drawing in the XQSM " ZGSM Plane showing thesituation at the start ofthe growth phase of the August 15,1968, substorm. The magnetic field had almost doubledby the end ofthe growth phase, so at that time the protonorbits were about half the size shown here.
-51-
80
CO
u0)r
O
OO
ClI
40
107
10C
r10g
rIO5
rIO
10"
-102 103
0600 UTI
9 R £
0700 0800
8
Universal time and radial distance
Fig. 43. East and west proton fluxes measured during the0714 UT August 15, 1968, substorm. The toppanel shows the scalar magnetic field variationduring the substorm. jie and jxw are the peakfluxes (average energies Pj =0 .12 MeV,?2 = 0.33 MeV, and P, = 0.81 MeV) measuredperpendicular to I? in the approximate east andwest directions. JQ is the value of the flux at theradial position of OGO-5 at pitch angles of about110 deg. .
-52-
gyro centers varied in position from
above the spacecraft to below the space-
craft. The complete scan took about
1 min; hence, every minute or so we
were able to generate a flux gradient by
assigning the measured fluxes to their
average position of motion. For perspec-
tive we show, in Fig. 43, a radial profile
of fluxes measured below the spacecraft
(j ), at the spacecraft (jQ), and above
the spacecraft (j. ). The flux gradient
history is shown in Fig. 44. The e-fold
boundary lengths and boundary velocities
are given in Figs. 45 and 46, respectively.
These data indicate that, in the region of
the midnight cusp where these data were
taken, the plasma sheet virtually col-
lapsed just prior to substorm expansion.
This observation has led to the sugges-
tion by McPherron et al. (1973) that
reconnection near the midnight cusp may
be the causitive factor in the initiation of
the substorm's expansive or explosive
phase.
We studied boundary motions during
several other substorms; a preliminary
account was presented by Buck et al.
(1972). In these studies, a steepening
XD
I'0'o
<u~° •£ «•O C I-
10"
• - 3 8 O IT) CO•fe <u or^-o>oLLI C— OO O
+1.0
10'
10
>,0706 AN^
i\ Vx0709
X0712
+0.5 -0.5
Z B~ R E
Fig. 44. Proton flux profile evolution during the substorm. Each set of curvesis a profile obtained from one full scan of the experiment aperture atthe indicated times. The thinning wave at the plasma sheet boundarybecame apparent about 0656 UT. The anticipated position of the neutralsheet (magnetic equator) is indicated at various times to the left. Thedata are representative of the flux in Pj in units of protons/cm^-sr-sec.The heavy line is Pj; the light lines are Po and P-$, the latter beinglonger. The P3 data after 0650 UT are deleted from the plots.
-53-
and thinning of the boundary always oc-
curred. However, in each case, OGO-5
was too high above the expected position
of the neutral sheet to determine the
extent of sheet collapse. Also, OGO-5
was deeper in the magnetotail than for
the 0714 UT August 15 substorm. These
data are not inconsistent, however, with
the suggestion that reconnection near the
midnight cusp may be the causitive factor
in substorm expansion.
THE APRIL 1969 SOLARPARTICLE EVENT
This interesting event (the largest
electron event ever recorded) was due to
a flare on April 10, 1969, behind the sun's
east limb. Figure 47 shows the time his-
tory of the electrons as observed on
10
: Well inside 5 §: sheet
IQ
0.1
0.01
}}•Boundary regionion I
»Thinning wave
0610 0630 0650 0710
Universal time
Fig. 45. The characteristic e-fold lengthsof the boundary. The data showboth the slowly varying regiondeep in the sheet and the boundarywave that-became appar'ent at-0656 UT.
E
i1c.9t3o>
rf\
Nc
*™
£"o_o
*oc3
£
Fig.
109
8
7
6
5
4
3
2
10
1 I . I 1 1Q
4lmsr
a r i n
/
a —
_
— D —a
— aa —
— —
— —
— —
I I 1 1 10630 0640 0650 0700 0710 0720 0730
Universal time
46. Boundary velocity perpendiculaito B (ZB-direction). The slowvariation is associated with thevariations deep in the sheetduring the early growth phase,whereas the rapid variationnear the end is associated withthe advance of the thinning.wave. The velocity in the•ZGSM direction was -0.9 ofthat shown in this figure.
OGO-5. Similar data have been obtained
for protons, but as yet we have done noth-
ing with these data. In contrast to west-
limb events, where the particles can take
advantage of the spiraling interplanetary
magnetic field in their transport to Earth,
the particles from this east-limb event
had to arrive at Earth by indirect means
(diffusion, convection, drift, etc.). It
would appear that this event is perfect for
the diffusive analysis of electron trans-
port, but our early attempts to this end
have not been successful. Possibly some
of the more recent theoretical formula-
tions will work.
By chance, during the course of the*
event, a similar magnetic spectrometer
A. L. Vampola, Space Physics Labo-ratory, The Aerospace Corporation, LosAngeles, California.
-54-
o(U
I>J
Ies
u
u0)
102
10
10-1
79keV
11 12 13 14 15
April 1969
16 17 18
Fig. 47. The time history of the April 1969 solar-particle event asobserved by the magnetic electron spectrometer on OGO-5.Data obtained in the magnetosphere that clearly representedtrapped radiation are excluded from this plot. Normally, thesolar fluxes could be identified well inside the magnetosphere,with no sign of discontinuity at the magnetospheric boundaryexcept for the superposition of trapped radiation.
was collecting data on the polar orbiting
Airforce Satellite OV1-19. This experi-
ment provided for good data correlation
(West and Vampola, 1971) between the
polar caps and the interplanetary region.
The two experiments tracked j. values
during the event's history. A compari-
son at the peak of the event is shown in
Fig. 48.
To summarize these observational data
data, we have:
(1) Absolute flux intensities and
energy spectra: There was tracking of
fluxes and spectra between the interplan-
etary region and over the north and south
polar caps during the entire history of the
event.
(2) Pitch-angle distributions: (a) The
interplanetary pitch-angle distributions
were isotropic. (b) The pitch-angle dis-
tributions over the polar caps were iso-
tropic except for the single loss cone
when looking towards Earth, (c) Sharp
discontinuities were observed in pitch-
angle distribution (energy-independent)
when transiting from the quasitrapping
region (double loss cone) to the polar
caps (single loss cone) on the sunward
-55-
IU
103
o4>
in1
-* 101CM
E0
«/>c20 10V
1•H
1
-110
: 1 — i — i i i 1 1 1 1 1 — i — i i i 1 1 1 1 1 — i — i i i 1 11.; April 13, 1969 :
i \ ' • i\X
: \, :: \ :r V . -- x "
- - *b ;
0910-0925 UT *
- o OGO-V \
: « QV1-19 V :
South polar cap \
1050-1 105 UT \
; • OGO-V ? '-+ ovi-i9 \ ' :
North polar capt ! | ! , ( ) , , ,
10 102 103 104
Energy — keV
Fig. 48. Comparison of electron-spectrometer data obtained onOGO-5 and OV1-19 near thepeak of the solar-particleevent on April 13, 1969. Forthe 0910-0925 UT data, OV1-19was over the south polar cap,altitude >4 500 km; for the1050-1105 UT data, it was overthe north polar cap, altitude<2000 km.
side of Earth, (d) Sharp discontinuities
were observed in pitch-angle distribution
(energy-independent) when transiting
from the outer zone to the polar cap at
local midnight.
(3) Polar flux profiles: (a) Uniform
particle distributions were observed over
the polar caps, (b) There were sharp dis-
continuities of particle fluxes in transit-
ing from quasitrapping region to polar
caps,
(4) Solar magnetic-field sector bound-
ary effects: No particle effects were
obvious at OGO-5 or OV1-19 during the
~1140 UT, April 13 interplanetary solar
magnetic sector crossing.
Observations 1, 2a, 2b, 2c, 3a, and
3b can be explained through a picture of
adiabatic motion. We allow the polar
field lines to connect to the solar field in
the interplanetary medium. The elec-
trons are expected to start off in the
interplanetary region where they are in
diffusive equilibrium, to spiral along the
field lines to the region over the polar
caps, then to mirror and return to the
interplanetary region. This picture is in
strong support of the model of the "open"
magnetosphere.
The pitch-angle and flux discontinuity
at the polar plateau (observations 2c and
3b) would at first glance appear to be a
crowning achievement of the "open" mag-
netosphere model. However, one would
anticipate no energy dependence in the
latitude of the pitch-angle discontinuity
(observation 2d), as .is found to occur
near local midnight. On April 13, near
the peak of the event, the transition
occurred at 64.89 ± 0.05'deg invariant
latitude for 50-keV electrons and 64.43
± 0.05 deg for 1.1-MeV electrons. Also,
there was no obvious effect in the OV1-19
data during the April 13 interplanetary
sector crossing, which occurred near the
peak of the particle event. In the pres-
ence of appreciable direct connection, we
would expect to find an effect due to re-
arrangement of the magnetic-field config-
uration. These two observations weaken
the arguments for the "open" magneto-
sphere model.
THE NOVEMBER 18, 1968SOLAR PARTICLE EVENT
A preliminary account of this work
was presented by D'Arcy et al. (1970).
-56-
This solar particle event was the result
of a west-limb flare. Relativistic pro-
tons were observed on Earth by neutron
monitors. OGO-5 was on the dusk side
of Earth, in position to observe the
scatter-free propagation of electrons and
protons along the spiraling interplanetary
magnetic field leading from the sun to the
vicinity of Earth. The early arrival is
shown in Fig. 49 by the scatter plot of the
EX electrons (79 keV). The data points
are shown in time sequence as the exper-
iment scanned about an axis (the earth's
radius vector, inclined about 34 deg to the
plane of the ecliptic), so that the experi-
ments aperture viewed largely in the
north-to-south direction. The experiment
looked somewhat west of the sun when
060 V DETECTOR ORBIT YEAR MONTH DAT YDAY LOAY HOUR flIN. SEC. RIMINIT. El 100 68 NOV 18 323 259 9 51 41.2 WFINAL CB> 12 9 M.I
«a riii «EcoR8 air A-O NEC nit RECi 11 ts itt 2 o
12 5 tO 940 0
8-
E+Oj
(4
w
gE*H
64
E»OJ
E-OtL * 4 8MfM ^ ^
HOURWH.RLMlKSEICSE•CSM•CSX
9"24
23.32823.545
5.2272.635.975.711.4
936
23.32623.543
5.2072.855.775.811.1
948
23.32223.542
5.2072.935.675.910.9
to0
23.31725.541
5.2373.035.576.010.7
1012
23.31125.542
5.2975.155.376.110.6
1024
23.30425.545
5.5873.235.276.110.4
1036
23.29523.545
5.4973.535.176.210.3
to48
23.28523.548
5.6273.534.976.310.3
I t0
23.27425.551
5.7875.634.876.410.3
M12
23.26123.556
5.9773.734.776.410.3
It24
23.24823.562
6.1773.834.576.510.3
1136
23.23323.568
6.4073.934.476.610.3
t t48
23.21623.577
6.6574.134.376.710.4
120
23.19925.588
6.9374.234.176.710.5
1212
0.0.0.
0.0.0.0.
Fig. 49. E, fluxes obtained during the early time history of the November 18, 1968,solar particle event.
-57-
viewing in the ecliptic plane. The upper
envelope of the data is due to electrons
arriving from the direction of the sun;
the lower envelope is the back-scattered
component. These data, including proton
data, are being analyzed by workers at
the Bartol Research Foundation, Swarth-
more, Pennsylvania.
HIGHLY -ANISOTROPIC PROTONDISTRIBUTIONS OBSERVEDINTERPLANETARY
Our experiment made numerous meas-
urements of highly-anisotropic proton
distributions in the interplanetary medium.
Some of these observations are associated
with a well-defined solar particle event;
OCO V DETECT*IN1T. PIFINAL PBt
ORBIT YEAR HONTH W YWY LOiY HOUR HIN. SEC. RUN REEL FILE RECORD KBIT A-0 REC MAC REC PACE94 68 HOY t 306 242 21 44 37.7 296 4 2 257 8KB 1 4 11
22 4 17.2 520 306 78
E-OI,
HOUR 21 "KIN. 44R 15.668L 26.947Ml 40.21WSE 66.0ICSE 52.1*SSH 69.1ICSH 45.6
2146
15.69626.948
40.1566.152.169.145.6
2148
15.72326.948
40.0966.252.069.245.6
2150
15.75126.94740.0366.352.069.345.6
fi13.77926.94639.9766.352.069.345.6
|i15.10626.94539.9166.431.969.445.5
fi15.13326.94339.1566.551.969.445.5
15.86126.94039.7966.651.969.545.5
220
15.18!26.93639.7366.751.869.645.5
22
15.91526.93239.6666.751.869.645.5
22
15.94226.92839.6066.851.869.745.4
226
15.96926.92339.5366.951.769.745.4
Fig. 50. Example of highly directed solar protons obtained on OGO-5. Note thatthese low energy protons (~100-150 keV) are directed along the field line.
-58-
KO V DETECTOR ORBIT YEAR HONTH DAT YDAY U)AY HOUR KIN. SEC. RUN RED. FILE RECORDINIT. PI 94 68 NOV 1 306 242 23 59 50.1 296 5 4 118FINAL FBI 25 59 29.6 iat
BJBO
KBIT A-0 REC HAG REC PACE8KB 1 4 6
363 9086400
E-01,
HOUR 23"HIM. 38R 17.142L 26.152XH 35.92•CSE 70.1•CSE 50.2•GSM 72.5«CSH 43.4
2340
17.16626.12635.83
70.150. t72.643.4
23
17J8926.10135.74
70.2S0.172.643.3
2344
17.21326.07935.64
70.350.172.743.3
2346
17.237235$
70.350.072.843.2
t17.26126.02339.46
70.450.072.843.1
1117.2152S.996J5.J7
70.550.072.943.1
17.301vs70.550.072.943.0
2354
17.33225.943
39.1870.649.973.042.9
2396
17.35525.91715.01
70.649.973.142.9
2358
17.57925.89034.99
70.749.975.142.8
240
0.0.0.0.0.0.0.
Fig. 51. Example of highly directed solar protons obtained on OGO-5. Note thatthese low energy protons (~100-150 keV) are directed along the field line.
a
I
Sa
others seem to be isolated bursts of .
protons lasting from minutes to tens
of minutes. During a well-defined solar
particle event, we find the usual in-
crease in anisotropy as we go to lower
energies. The lowest-energy channels,
however, can show high degrees of
anisotropy. In the cases we examined,
the protons may be observed coming
from roughly the solar direction. Other
examples of large anisotropy are shown
in Figs. 50 and 51. These data were
acquired during the solar particle event
accompanying the intense magnetic
storms of October 31- November 1,
1968.
-59-
Concluding Remarks
This experiment made significant
advances in several areas:
• The electron distributions and
dynamics of the inner belt were
provided for 1968 and 1969. These
data will be useful in studying the
diffusive transport of particles in
the inner magnetosphere.
• A partial study was carried out
covering the electron pitch-angle
distributions and dynamics of the
slot and outer belt regions.
• A rather complete survey was
made of the electron pitch-angle
distributions throughout the equa-
torial regions of the outer magneto-
sphere, with special insight into
magnetopause-shadowing drift-shell
effects, field-configuration-change
drift-shell-splitting effects, and
substorm effects. These data pro-
vide a good view of the azimuthal
drift motions of electrons in the
distorted-field regions of the outer
magnetosphere. .
• Detailed motions of the plasma
sheet in the tail were observed dur-
ing a substorm, using the proton
east-west effect. These data show
the almost complete collapse of the
tail field prior to substorm
expansion for the case studied.
• The transport of solar electrons to
the polar caps was studied via cor-
relative data from both the OGO-5
and OV1-19 satellites. These data
provide insight into magnetospheric
structure.
There is still considerable work to be
done with our OGO-5 data that we believe
to be significant:
• The detailed organization of the slot
and the outer-belt data needs to be
completed so that theoreticians can
study the transport problem in the
trapping regions following storm-
time injection (our inner belt data
already are organized adequately).
• Electron pitch-angle distributions
need to be studied more thoroughly
in light of the recent theoretical
advances in our understanding of
pitch-angle diffusion in the
plasmasphere.
• Electron and proton distributions
need to be studied near the noon
magnetopause to assess their azi-
muthal drift motions through
minimum-B regions in the earth's
magnetic field.
• Electron pitch angles need to be
studied more thoroughly in the pre-
midnight magnetosphere to permit
better understanding of the pitch-
angle signature in the study of mag-
netic field topology,, especially with
regard to substorms.
• A complete survey of proton pitch-
angle distributions needs to be con-
ducted at all local times in the
equatorial regions.
• The proton east-west effect needs
to be exploited more fully in the
study of plasma-sheet dynamics,
especially during substorms. This
seems to be the most effective way
of studying boundary motions on a
single satellite.
• The manner in which electrons
drift azimuthally through the region
-60-
of the midnight cusp so as to main-
tain some semblance of the butter-
fly pitch-angle distribution needs to
be understood. This will provide\
additional insight into field topology
for dynamic and static periods.
• Well-defined plasma sheet oscilla-
tions, observed past midnight in
terms of particles and B-fields,
need to be understood. Are these
effects associated with the solar
wind?
• The appearance of energetic elec-
trons and protons in the magneto-sheath near the high latitude mag-
netopause needs to be understood.
There may be a tie-in to reconnec-
tion.
• The highly directed solar protons
observed interplanetary need to be4
investigated. Do these low energy
particles follow the convective
flow of the solar wind?
• The scatter-free propagation of
solar electrons from the sun to the
earth needs to be investigated fur-
ther in order to enhance our under-
standing of particle transport.
• The April 1969 solar particle event
needs to be understood more thor-
oughly in terms of particle trans-
port. As a follow up on this work,
there are several other events that
should be studied.
• The manner in which solar protons
gain access to the near-earth trap-
ping regions (~3 RE> needs to be
understood.
The above list is by no means com-
plete. This experiment has provided a
veritable goldmine of information. It is
hoped that a significant portion will reach
the printed page.
Acknowledgments
Many people contributed to the suc-
cess of this experiment. Those assist-
ing in the construction phase are cited
in the instrument report. In the data
reduction and analysis phase, we acknowl-
edge the continued support of E.
Mercanti (Program Manager), K. Meese
(Program Coordinator), J. Meenen
(Operations), and H. Lindner (Data
Processing) of GSPC. We thank P. J.
Coleman and C. T. Russell of UCLA for
the ready availability of their OGO-5
vector magnetometer data. In addition,
we thank C. T. Russell, R. L. McPherron,
Margaret G. Kivelson, and T. A. Farley,
all of UCLA, for many stimulating dis-
cussions during the course of data
analysis.
The people directly assisting the auth-
ors at Lawrence Livermore Laboratory
were M. M. Zeligman and Bettie Myers.
They were responsible for handling the
large amounts of data produced by the
experiment. R. G. D'Arcy, Jr., who was
responsible for the proton spectrometer
while at Livermore, has continued with
the data reduction of these data at the
Bartol Foundation.
The work covered in this report was
performed under the auspices of the U. S.
Atomic Energy Commission, funded in
part by NASA under P. O. S-70014-G.
-61-
References
Buck, R.M., H.I. West, Jr., and R. G. D'Arcy, Jr., "Evidence for thinning of the
plasma sheet during the August 15, 1968 substorm," EOS Trans. Amer.
Geophys. Union 51, 810, 1970.
Buck, R. M., H.I. West, Jr., and R. G. D'Arcy, Jr., "Energetic protons as probes of
magnetospheric particle gradients," EOS Trans. Amer. Geophys. Union 53,
486, 1972.
Buck, R.M., H.I. West, Jr., and R. G. D'Arcy, Jr., "Satellite studies of magneto-
spheric substorms on August 15, 1968: 7. OGO-5 energetic proton observa-
tions —Spatial boundaries," J._GejDp_h^s,._JRe_s_. 78, 3103, 1973.
Fairfield, D. H., "Average magnetic field configuration of the outer magnetosphere,"
J. Geophys. Res. 73, 7329, 1968.
Haskell, G. P., "Anisotropic fluxes of energetic particles in the outer magnetosphere,1
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Lyons, L. R., R. M. Thorne, andC.S. Kennel, "Pitch angle diffusion of radiation belt
electrons within the plasmasphere," J. Geophys. Res. 77, 3455, 1972
McPherron, R. L.( M. P. Aubry, C.T. Russell, and R. J. Coleman, "Satellite studies
of magnetospheric substorms on August 15, 1968: 9. Phenomenological models
for substorms," J. Geophys. Res. 78, 3131, 1973.
McQuaid, J. H., "An electron and proton spectrometer detector system for an OGO-E
satellite experiment," IEEE Trans. Nucl. Sci. NS-13 No. 1. 515, 1966.Pfitzer, K., "The spectra and intensity of electrons in the radiation belts," Space Rej^.
6_, 702, 1966. .
Pfitzer, K. A., and J. R. Winkler, "Experimental observation of a large addition to the
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1968.
Roederer, J. G., "On the adiabatic motion of energetic particles in a model magneto-
sphere," J. Geophys. Res. 72, 981, 1967.
Roederer, J. G., "Quantitative models of the magnetosphere," Rev. Geophys. 77, 77,
1969. .
Serlimitsos, P., "Low energy electrons in the dark magnetosphere," J. Geophys. Res.
7J_, 61, 1966.
Shabansky, V. P., "Some processes in the magnetosphere," Space Sci. Rev. 12, 299,
1971.
Speiser, T. W., "Particle trajectories in model current sheets: (Part 1). Analytical
solutions," J. Geophys. Res. 70, 4219, 1965.
Speiser, T. W., "Particle trajectories in model current sheets: (Part 2). Aplications
to auroras using a geomagnetic tail model," J. Geophys. Res. 72, 3919, 1967.
Speiser, T. W., "The Dungey model of the magnetosphere, and astro-geophysical
current sheets," Radio Sci. 6, 315, 1971.
-62-
Sugiura, M., B. G. Ledley, T. L. Skillman, and J. P. Heppner, "Magnetospheric-field
distortions observed by OGO-3 and 5," J. Geophys. Res. 76, 7553, 1971.
West, H. I., Jr., L. G. Mann, and S. D. Bloom, "Some electron spectra in the radiation
belts in the Fall of 1962," Space Res. 5, 423, 1965.
West, H. I., Jr., "Some observations of the trapped electrons produced by the Russian
high altitude nuclear detonation of October 28, 1962," in Radiation Trapped in the
Earth's Magnetic Field (B. M. McCormac, ed.), Dordrecht, Holland: D. Reidel
Publishing Company, 634, 1965.
West, H. I., Jr., J. H. Wujeck, J. H. McQuaid, N. C. Jenson, R. G. D'Arcy, Jr., R.W.
Hill, and R. M. Bogdanowicz, "The LRL electron and proton spectrometer on
NASA's Orbiting Geophysical Observatory V(E) (instrumentation and calibra-
tion)," Lawrence Livermore Laboratory, Rept. UCRL-50572, June 1969.
West, H. I., Jr., R.W. Hill. J. R. Walton, R. M. Buck, and R. G. D'Arcy, Jr.,
"Electron and proton pitch-angle distributions in the outer magnetosphere,"
EOS Trans. Amer. Geophys. Union 50, 659, 1969.
West, H. I., Jr., R. M. Buck, and J. R. Walton, "Electron spectra in the slot and the
outer radiation belt," EOS Trans. Amer. Geophys. Union 51, 806, 1970.
West, H. I., Jr., R. M. Buck, and J. R. Walton, "The butterfly pitch-angle distribution
of electrons in the postnoon to midnight region of the outer magnetosphere as
observed on OGO-5," EOS Trans. Amer. Geophys. Union 53, 486, 1972a.
West, H. I., Jr., R. M. Buck, and J. R. Walton, "Shadowing of electron azimuthal-drift
motions near the noon magnetopause," Nature Phys. Sci. 240, 6, 1972b.
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substorms on August 15, 1968: 6. OGO-5 energetic electron observations —
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78, 3093, 1973b.
-63-
Distribution
LLL Internal Distribution
Roger E. Batzel
J. S. Kane
W. E. Nervik
H. L. Reynolds
J. E. Carothers
J. N. Shearer
R. D. Neifert
H.I. West, Jr.
R. M. Buck
J. R. Walton
LBL Library
TID File
External Distribution
100
30
K. MeeseE. MercantiOffice of DirectorOffice of Assistant Director, Projects 3Office of Assistant Director, T&DS 3
Office of Assistant Director, SSOffice of Technical ServicesLibraryNegotiatorTechnical Information DivisionNational Space Science Data CenterTechnical DirectorGoddard Space Flight CenterGreenbelt, Maryland
M. PomerantzThe Bartol Research Foundation
of the Franklin InstituteSwarthmore, Pennsylvania
R. G. D'Arcy, Jr.Cambridge, Massachusetts
A. SchardtE. SchmerlingL. KavanaughCode SGNASA HeadquartersWashington, D. C.
Technical Information CenterOak Ridge, Tennessee
332
57
NOTICE
"This report was prepared as an account of work sponsored bythe United States Government. Neither the United Stales northe United States Atomic Energy Commission, nor any of theiremployees, nor any of their contractors, subcontractors, or theiremployees, makes any warranty, express or implied, or assumesany legal liability or responsibility for the accuracy, completenessor usefulness of any information, apparatus, product or processdisclosed, or represents that its use would not infringe privately-owned rights."
CSM/rt/edas
-64-