The MIT Faraday cup experiment on IMP 8 measures
currents from solar wind ions, and from these measurements we calculate
the velocity, density, and temperature of the solar wind. The IMP 8 data
files consist of fine resolution data (approximately 1 minute resolution).
IMP 8 spins with a period of approximately 2.7s. The Faraday
Cup (FC) instrument scans the solar wind distribution stepping through a
contiguous set of energy windows, one step per spacecraft spin. The FC
instrument divides the spin into thirty-two, 11.25 degree angular sectors
and integrates the measured currents over different angular sectors
depending upon the Mode in which the instrument is operating. The border
between two of the 11.25 degree angular sectors lies on the Sun-spacecraft
line.
The FC sensor collector plate is divided into two,
semi-circular halves; the division line is parallel to the spacecraft spin
plane which is approximately parallel to the ecliptic plane. The split
collector allow determination of the bulk plasma flow relative to the spin
plane; North/South angles refer to flows coming from above or below the
spin plane respectively (flows from the South are designated as having a
positive N/S angle).
The bulk flow angle in the spin plane is determined from the
measurements of current vs. rotation angle. The currents telemetered to
the ground are the sums of currents for the two half-collectors ("A" and
"B") and, for the TMS and AQM modes, also the current for the
half-collector "B".
Electrons are measured except for the eight angles near the Sun.
The experiment has two memories only one of which is operating
perfectly. As a result, only every other TMS spectrum is usable, and the
time between spectra is usually twice that that would be expected from the
spacecraft spin rate. The bad half-memory also limits the energy windows
that can be used in the other modes, since they require both memories to
hold the data. On occasion, the data are read out rapidly enough by the
spacecraft to allow repeated use of the good half-memory, and the time
resolution in the TMS is approximately 32 seconds.
Version:2.2.9
The MIT Faraday cup experiment on IMP 8 measures
currents from solar wind ions, and from these measurements we calculate
the velocity, density, and temperature of the solar wind. The IMP 8 data
files consist of fine resolution data (approximately 1 minute resolution).
IMP 8 spins with a period of approximately 2.7s. The Faraday
Cup (FC) instrument scans the solar wind distribution stepping through a
contiguous set of energy windows, one step per spacecraft spin. The FC
instrument divides the spin into thirty-two, 11.25 degree angular sectors
and integrates the measured currents over different angular sectors
depending upon the Mode in which the instrument is operating. The border
between two of the 11.25 degree angular sectors lies on the Sun-spacecraft
line.
The FC sensor collector plate is divided into two,
semi-circular halves; the division line is parallel to the spacecraft spin
plane which is approximately parallel to the ecliptic plane. The split
collector allow determination of the bulk plasma flow relative to the spin
plane; North/South angles refer to flows coming from above or below the
spin plane respectively (flows from the South are designated as having a
positive N/S angle).
The bulk flow angle in the spin plane is determined from the
measurements of current vs. rotation angle. The currents telemetered to
the ground are the sums of currents for the two half-collectors ("A" and
"B") and, for the TMS and AQM modes, also the current for the
half-collector "B".
Electrons are measured except for the eight angles near the Sun.
The experiment has two memories only one of which is operating
perfectly. As a result, only every other TMS spectrum is usable, and the
time between spectra is usually twice that that would be expected from the
spacecraft spin rate. The bad half-memory also limits the energy windows
that can be used in the other modes, since they require both memories to
hold the data. On occasion, the data are read out rapidly enough by the
spacecraft to allow repeated use of the good half-memory, and the time
resolution in the TMS is approximately 32 seconds.
| Role | Person | |
|---|---|---|
| 1. | PrincipalInvestigator | spase://SMWG/Person/Alan.J.Lazarus |
| 2. | TeamMember | spase://SMWG/Person/John.D.Richardson |
Text created by MIT IMP8 plasma team
In CDF via HTTP from SPDF
With subset, plot and list functionalities
With subset, plot and list functionalities
Time
Spacecraft flag (6/7/8 = IMP 6/7/8)
Decimal year
Region flag provides an estimate of the region from
which the data came.
There are three flag values:
* 1 - This time is definitely solar wind.
* 2 - This time is either solar wind or magnetosheath, with no
differentiation being made. This designation is used for multiple crossings
between the solar wind and sheath regions.
* 3 - This time is definitely NOT solar wind, being either
magnetosheath or magnetospheric data.
Indicates the operating mode of the experiment. The following table describes the measurements for each mode.
+---------------------------------------------------------------------------------------------------------+
| Mode | Mode | Angles number | Currents | Energy windows | Energy windows |
| Number | Name | [deg] | | Protons | Electrons |
|-----------------|----------------|------------------|-----------|------------------|--------------------|
| 2 | Tracking (TMS) | eight: 11.25 centered on Sun-spacecraft line; six: 45 for remainder of spin | A+B and A | 8* | 4 |
| 3 | Acquisition (AQM | same as TMS | same as TMS | 24 | 21 |
| 1 | Non-tracking (NTMS) | eight, 45 | A+B only | 24 | 21 |
+---------------------------------------------------------------------------------------------------------+
*Selected so that the peak flux energy step of the prior distribution is the 3rd step of this measurement.
Note that the mode names are historical and confusing: the NTMS mode has the greatest sensitivity because
of the 45 degree angular sectors and hence longer integration times, but all the energy windows won't fit into the
working side of our on board memory. So all the parameters will be in modes 2 or 3. In order to reduce the time
between spectra, in the TMS mode the eight lowest electron energy windows are covered using four sets of two windows
of increasing energy; those eight electron windows are thus covered in a sequence of four TM spectra.
Spacecraft position in GSE coordinates
Spacecraft position Y-component in GSM coordinates
Spacecraft position Z-component in GSM coordinates
(Better, from fits) Ion Flow Velocity (aberration corrected)
(From moments) Proton Flow Velocity (no aberration
correction)
(Better, from fits) Proton most-probable thermal
speed (aberration corrected). Thermal speed is the most probable thermal
speed (i.e., the square root of [2kT/m(proton)]). To convert thermal speed
to temperature in eV, multiply 0.0052 by the square of the thermal speed;
to convert to temperature [K], multiply the square of the thermal speed by
60.5.
(From moments) Proton most-probable thermal speed (no aberration
correction). Thermal speed is the most probable thermal speed (i.e., the square
root of [2kT/m(proton)]). To convert thermal speed to temperature in eV, multiply
0.0052 by the square of the thermal speed; to convert to temperature [K], multiply
the square of the thermal speed by 60.5.
(Better, from fits) Proton number density
(From moments) Proton number density
(Best, from fits) Proton East/West flow angle
(aberration corrected). Azimuth is E/W, meaning bulk flow from the East
or the West side of the Sun respectively. Positive azimuth angle means
flow from the West.
(From moments) Proton East/West flow angle (no
aberration correction). Azimuth is E/W, meaning bulk flow from the East
or the West side of the Sun respectively. Positive azimuth angle means
flow from the West.
(Better, from fits) Proton flow elevation angle
(aberration corrected) from North or South of the spacecraft spin plane
(almost identical to the plane of the ecliptic).Positive elevation angle
means flow from the South. Threshsp values are determined from currents
greater than a threshold value, below which we are not confident about
the contribution of noise.
(From moments) Proton flow elevation angle (no
aberration correction) from North or South of the spacecraft spin plane
(almost identical to the plane of the ecliptic).Positive elevation angle
means flow from the South. Thresh values are determined from all
currents.