Mar 26, 1976 - ranged from 4 to 7 for the two adjacent three hour periods and rose to 8 in the 3rd three hour period. .... 3 span 2 km at an average altitude of.
Vol.
4, No. 2
Geophysical
HIGH
RESOLUTION
ELECTRON
Research Letters
ENERGY SPECTRA
IN
AN ACTIVE
Departments of Chemistry and Physics,
Abstract.
cipitating measured
The spectrum
auroral at
of high
electrons
altitudes
from
J.P.
and P. D. Feldman
the
Baltimore,
Maryland 21218
slit. The background count rate at energies other than the energy of the incident electron beam was found to be negligible for the purposes of the present rocket experiment. In operation, the outer sphere was grounded to the body of the rocket and the inner sphere swept linearly from 0 to 3000 volts (0 to 26 keV electrons) in 128 steps. Two seconds were required for a complete
energy prekm at
1976
The Johns Hopkins University,
(2-26 keV) was
97-175
Doering
1977
AURORA AT THE ONSET
OF THE MAGNETIC STORM OF MARCH 26,
D. A. Edmonson, W. K. Peterson,
February
on-
set of the magnetic storm of 26 March 1976 by a rocket borne experiment launched from Ft. Churchill, Manitoba. The spectra show an unusual double-peaked distribution, with maxima at 4.5 and 17 keV, that persists for the full four minutes of data acquisition. Multiple structure within the main peaks is also noted. The ener-
energy placed
sweep. between
A slit biased the exit slit
at -100 volts was and a Johnston
gies and intensities of the two peaks observed at 163 km and 0 ø pitch angle vary independently during a sudden brightening on the downleg of the rocket flight. Thirty spectra taken during a slow roll maneuver near apogee show that the pitch angle distribution for the two peaks in the energy spectrum is isotropic over both the precipitating and backscattered hemispheres.
Laboratory MM-1 electron multiplier to prevent secondary electrons generated inside the deflec•tor from reaching the multiplier. The defocusing action of this slit prevents reliable
Spectra taken near the end of the flight show energy dependent attenuation with altitude but fluctuations in auroral intensity preclude a detailed analysis.
oriented so that the long axis of the entrance slit was parallel to the rocket axis and the look direction tangent to the rocket body.
measurement
of the
spectra
below
2 keV.
In
flight, the spectrometer head was deployed on arms and locked into place with the slit 15 cm from
the
rocket
skin.
The
sensor
head
was
Experiment Introduction
The experimental
Churchill,
Manitoba
2:58:26.5
bright,
UT.
The
diffuse
on March 26, rocket
auroral
was
1976 at
launched
into
a
served pitch angles for the 0-26 keV electron spectrometer: 1) from T = +90 to 165 sec: the rocket axis was aligned with the magnetic field lines, pitch angle of observed primary flux, • = 90ø; 2) T--+165 to 183 sec: the rocket
26-27 March1976. The planetary Kp index
very quiet having daily Kp sumsof 11 or less.
yawed 90ø, sighting the rocket axis into the eastern horizon, e = 90 ø - 164ø; 3) T = +198 to 257 sec: the payload performed a slow 197 ø roll (3.31 deg/sec), e-- 164 ø - 180ø-0 ø. The ob-
Instrument
5.00
spectrometer
cm and 5.30
90 ø arc The exit
consisted
90 ø x 90 ø spherical cm.
of radius slit
was calibrated
was
5.12
of two
segments of radii
The entrance
slit
served pitch
was a
in the laboratory
The instrument
using a mono-
due
determined area factor was 2.75 x 10-• cmZ-str while the energy resolution, AE/E, was found to be 1.5%, independent of position on the entrance
6L0730.
was then
south.
Data
An energy-time spectrogram of the primary spectrometer data is presented as a gray shade
Copyright 1977 by the American Geophysical Union. number
electrons
the period T = +90 to 365 sec was ~200 m sec-1
energetic electron source. The expertmen_tally
Paper
angle of primary
held at 0 ø until the end of data acquisition at T = +365 sec. Apogee was reached at T = +222 sec and 175.8 km. The downrange velocity during
cm and was 1 mm wide.
1 cm x 1 ram.
UV
eV and 0-26 keV with look axes tangent to the rocket body and 180 ø with respect to each other. Some of the data acquired with the other instruments has already been described [Park et. al., 1976]. The payload was equipped with an attitude control system which despun the rocket after burnout and performed the following maneuvers which resulted in the following ob-
ranged from 4 to 7 for the two adjacent three hour periods and rose to 8 in the 3rd three hour period. The five days prior to this time were
The electron
three
along the rocket axis, as well as the two electron spectrometers covering the ranges 1 to 80
arc of 60 kR [01115577
intensity (at the time of the launch), which was moving rapidly in an east-west direction. Ground based photometry and all-sky photography were not possible after T + 60 seconds because of the ill-timed appearance of cloud cover above the launch site. The sudden appearance of the arc coincided with the first large scale deviations of the ground based magnetometers that marked the onset of the large magnetic storm of
concentric
package contained
spectrometerscoveringthe range 700 % to 2800 •, a six barrel photometer to monitorthe emissions at 3371•, 3914%, 5577•, 6685•, 7319% and 7620•, andan IR spectrometer,all sighted
The experiment was carried aboard an Aerobee 170 rocket (NASA 13.077UA) launched from Ft.
75
76
Edmonson
et
al.:
Electron
Energy 180
180
Spectra
--
--
'"" 130 -..;
