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L O W E N E R G Y P A R T I C L E S D A T A S E T


1. INTRODUCTION

This data set contains fluxes and pitch angles (relative to measured
magnetic field) of protons and electrons as measured in the lower half
of the energy steps of the electrostatic analyzers, that is, at "<10 ev,"
40 eV and 0.76 keV, 60 eV and 1.2 keV, and 100 eV and 1.8 keV. The
indicated pairings correspond to simultaneous measurements in the low
and medium energy analyzers. Time resolution is variable according to
the memory mode being used at any time, ranging between 10 msec and
2.56 sec. Each data file corresponds to one memory readout, and
typically consists of a few continuous-data segments. The first
several records in each file constitute a header giving the time spans
of the segments, the energy step, and other common information. The
data records, in ASCII, also contain spacecraft position data.

Time span of data set: 81-10-01 - 82-03-01
Time span for every file is given in "PARTICLE.TAB" file


2. SHORT DESCRIPTION OF INSTUMENT

Particle detector RIEP-2802 was developed and built in Russia. It
is 4-channel electrostatic spectrometer with spectral resolution
(deltaE)/E ~ 0.2. The aperture angle was 0.036 sterad, geometric
factors from 0.092 to 0.089 cmsq x sterad for different units.
Two detector channels were for electrons, two channels for ions,
all working in parallel. Among 8 energy steps possible only four
were used in the seances presented below. They are identified in
the heading of respective data column in each data file by the
particles' central energy for each of the 4 detectors (NSTEP
ranging from 0 to 3, see Table 2.1).
For a detailed description see Galperin et al., Annales de
Geophysique, v.38, N 5, p. 583, 1982.

The Table 2.1. gives the respective central energies for these
energy steps (NSTEP):

Table 2.1.
-----------------------------------------------------------------
NSTEP: Low energy : Low energy : Medium energy : Medium energy
:electrons (eV): ions (eV) : electrons(keV) : ions (keV)
-----------------------------------------------------------------
0 <10 <10 <0.01 <0.01
1 40 40 0.76 0.76
2 60 60 1.20 1.20
3 100 100 1.80 1.80
-----------------------------------------------------------------

Note: NSTEP for every file is given in accompaning "PARTICLE.TAB" file.

In the data files the values of the particle number flux is given
in the data columns in units: particles per square cm per second
per steradian per keV. Also given are the NSTEP code (in most of
the seances, but not always, unchanged during a telemetry mode
within a seance), and pitch-angle (angle between the local magnetic
field direction and the particle velocity along a particular detector
axis) for the registered electrons (ae) and ions (ie). These angles
are evaluated from the onboard magnetometer data.

Please, note that in a data file the first 1-7 rows usually give
spurious data due to telemetry and instrument switched and
decoding programs adjustments, AND THUS MUST BE DISCARDED.

Besides, the locations of the typical particle precipitation
boundaries deduced from the above channels and other particle
detectors onboard, together with their INVARIANT
LATITUDE/MAGNETIC LOCAL TIME, and definitions of the boundaries,
are given in the separate file PRECBORD.TXT.


3. FILES AND FORMAT DESCRIPTION


3.1. Name of files

The filename of data files contains the number of the memory readout seance
followed by the letters "a3k". It has ".dat" exrention.

Each data file has a header and number of data records.

Logical data record -131 bytes +Cr/LF

3.2. Record format description

WORD ASCII MEANING UNITS/COMMENTS


1 I4 Hour (0-23)
2 I3 Minute (0-59)
3 I3 Second (0-59)
4 I4 Millisecond

5 E12.3 Number flux, low energy electrons number/cmsq sec sr keV

6 E10.3 Number flux, low energy ions number/cmsq sec sr keV

7 E10.3 Number flux, medium energy electrons number/cmsq sec sr keV

8 E10.3 Number flux, medium energy ions number/cmsq sec sr keV

9 F6.0 Pitch-angle ae between magnetic Degrees, 0-180
field and mean electron velocity (downward: 0 in Northern
Hemisphere, 180 in
Southern Hemisphere)

10 F6.0 Pitch-angle ai between magnetic Degrees, 0-180
field and mean ion velocity (downward: 0 in Northern
Hemisphere, 180 in
Southern Hemisphere)

11 F8.1 Altitude km

12 F8.2 Geographic Latitude of the Degrees, +/-90
Spacecraft

13 F8.2 Geographic Longitude of the Degrees, 0-360
Spacecraft

14 F8.2 L, McIlwain's Invariant Magnetic Earth's Radii
Drift Shell Parameter

15 F8.2 L0, Invariant Latitude Degrees, +/-90
L0=arc cos (sqrt(1/L))

16 F7.2 MLT, Magnetic Local Time Hours.decimal hours
(for centered dipole field)

17 F8.3 BMAG, Module of IGRF80 Magnetic MilliGauss
Field (1 milliGauss=100nT)

18 F8.2 ZSUN, Solar Zenith Angle Degrees, 0-180
---------------------------------------------------------------------------
The parameters 8-15 were calculated with
the CADR4 program developed in IKI for orbital and geophysical
reference information for near-Earth satellites (Galperin et
al., Preprint IKI (in Russian), Pr 544, 1980).


3.3. STRUCTURE OF A HEADER

The header starts with a title:
"PASSPORT FOR THE SEANCE S-XXXX, ARCAD-3".
It gives (in place of XXXX) the number of the memory readout
telemetry seance and the time intervals of the data recording.

The first header text paragraph starts with a row "THE NUMBER OF
THE TIME INTERVALS - YY". It gives (instead of YY) the number of
uninterrupted memory recordings, each one in a particular memory
mode ZAP (described in GENERAL.TXT). Each such recording is
described as a line in the "PASSPORT...". Within a data file it
corresponds to a number of lines each describing a "measurement
point" by a line of the data. The number of measurement "points"
(from the start to the end of each recording) is shown in two first
columns of each line, the next columns give the date (dd.mm.yy)
and the UT time (hh.mm.ss.mss) of the start of the interval, then
the same for the end of an interval. The before last column of a
passport row gives the DT - a data time step in milliseconds
(mss), and the last column gives the memory mode ZAP (1-4).

In the second heading paragraph, a reminder is given that
the first rows (up to 7) with the data in each time/ZAP interval
may be false due to telemetry switches, etc., AND THUS MUST BE
DISCARDED.

The third text paragraph in a file heading contains a reminder
of the relevant data contained in the files and the units of
the particle number flux:
particles per cm^2 per sec per ster per keV.

The "NSTEP=X" gives (instead of X) the energy step number during
this time interval, the NSTEP, as described in the Table 2.1.
above. The NX=ZZZZZ - gives (by ZZZZZ) the total quantity of the
rows in the data file, or the number of the measurement points
registered. Some of them can be erroneous due to telemetry noise,
so the real quantity of the rows can be lower, or equal, to the NX
quantity.

The headings of each data column within a data file are
provided, which contain the meaning of the data in the column
(see Format Description above).

As the date of measurements in a data file for each time
interval is given in the "PASSPORT OF THE SEANCE", it is
not repeated in the data rows, and only the UT is given.
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