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IMP 8 MIT Full Resolution Definitive Interplanetary Plasma Data

ResourceID
spase://NASA/NumericalData/IMP8/PLS/PT01M

Description

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.

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Version:2.2.9

NumericalData

ResourceID
spase://NASA/NumericalData/IMP8/PLS/PT01M
ResourceHeader
ResourceName
IMP 8 MIT Full Resolution Definitive Interplanetary Plasma Data
AlternateName
IMP 8 Solar Wind Plasma Faraday Cup Data
ReleaseDate
2020-07-07 21:14:39Z
Description

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.

Acknowledgement
For papers and presentations using these data, please acknowledge the MIT Space Plasma Physics Group and the path through which you accessed the data.
Contacts
RolePerson
1.PrincipalInvestigatorspase://SMWG/Person/Alan.J.Lazarus
2.TeamMemberspase://SMWG/Person/John.D.Richardson
InformationURL
Name
Readme file at SPDF
URL
ftps://spdf.gsfc.nasa.gov/pub/data/imp/imp8/plasma_mit/sw_msheath_min/00readme.txt
Description

Text created by MIT IMP8 plasma team

PriorIDs
spase://VMO/NumericalData/IMP8/PLS/PT01M
spase://VSPO/NumericalData/IMP8/PLS/PT01M
AccessInformation
RepositoryID
spase://SMWG/Repository/NASA/GSFC/SPDF
Availability
Online
AccessRights
Open
AccessURL
Name
FTPS from SPDF (not with most browsers)
URL
ftps://spdf.gsfc.nasa.gov/pub/data/imp/imp8/plasma_mit/
AccessURL
Name
HTTPS from SPDF
URL
https://spdf.gsfc.nasa.gov/pub/data/imp/imp8/plasma_mit/
Description

In CDF via HTTP from SPDF

Format
CDF
AccessInformation
RepositoryID
spase://SMWG/Repository/NASA/GSFC/SPDF
Availability
Online
AccessRights
Open
AccessURL
Name
CDAWeb
URL
https://cdaweb.sci.gsfc.nasa.gov/cgi-bin/eval2.cgi?dataset=I8_H0_MITPLASMA&index=sp_phys
ProductKey
I8_H0_MITPLASMA
Description

With subset, plot and list functionalities

AccessURL
Name
FTPBrowser
URL
https://omniweb.sci.gsfc.nasa.gov/ftpbrowser/imp_mit_min.html
Description

With subset, plot and list functionalities

Format
Text
ProcessingLevel
Calibrated
ProviderVersion
v01
InstrumentIDs
spase://SMWG/Instrument/IMP8/PLS
MeasurementType
ThermalPlasma
TemporalDescription
TimeSpan
StartDate
1973-10-31 20:10:26
StopDate
2006-07-26 17:10:34
Cadence
PT01M
ObservedRegion
Heliosphere.NearEarth
ObservedRegion
Earth.Magnetosheath
Caveats
The cadence varies slightly (by a few seconds) and is approximately 1 minute. The parameter values are derived from taking moments of the distributions and from fits to the distributions. As can be seen easily by eye, there is some discrepancy between moments and our best (fit) parameters; moments are definitely less accurate. Use moment values with caution, and PLEASE request assistance or clarification. For the moment parameters, changes in value are more trustworthy than absolute values, but nothing is guaranteed to be accurate. A value of 9999.0 means that we couldn't calculate that parameter. All parameters are based on a convected, isotropic Maxwellian model. The moment values, for angles and for the speed, do NOT have aberration corrections included. This means that the total speeds are slightly too low, and that the angles are not really correct. In particular, the azimuthal (E/W) angle is about 4 degrees too positive; this can clearly be seen where both nonlinear and moment angles are available. If good angles cannot be obtained, there won't be any velocity components; speeds are available in some such cases. Dr. Joseph King (NASA/GSFC) has looked at 27-day averages of OMNIWeb data from 1984-1994. He finds (and the MIT team agrees) that there is an offset of about +2 degrees (from the South) in the N/S angle and an annual variation of that angle with an amplitude of about 1 degree. The MIT team believes that the annual variation is due to a tilt of the s/c spin axis. He found the mean flow longitude in that study to be -0.3 degrees with no obvious annual variation.
Parameter #1
Name
Time
ParameterKey
Epoch
Description

Time

Caveats
The cadence varies by a few seconds and is approximately 1 minute. ValidMin and ValidMax values in the CDF files are incorrect, do not use.
FillValue
-1.0E31
Support
Qualifier
Scalar
SupportQuantity
Temporal
Parameter #2
Name
Spacecraft
ParameterKey
Spacecraft
Description

Spacecraft flag (6/7/8 = IMP 6/7/8)

ValidMin
0
ValidMax
8
FillValue
9
Support
SupportQuantity
Other
Parameter #3
Name
Decimal Year
ParameterKey
decimal_year
Description

Decimal year

ValidMin
1972.0
ValidMax
2020.0
FillValue
100000.0
Support
Qualifier
Scalar
SupportQuantity
Temporal
Parameter #4
Name
Region
ParameterKey
Region
Description

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.

ValidMin
1
ValidMax
8
FillValue
9
Support
SupportQuantity
Other
Parameter #5
Name
Operating mode
ParameterKey
mode
Description

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.

ValidMin
1
ValidMax
8
FillValue
9
Support
SupportQuantity
Other
Parameter #6
Name
Spacecraft Position GSE
ParameterKey
SC_Pos_GSE
Description

Spacecraft position in GSE coordinates

Units
Re
UnitsConversion
6.378e6>m
CoordinateSystem
CoordinateRepresentation
Cartesian
CoordinateSystemName
GSE
Structure
Size
3
Element
Name
Xgse
Qualifier
Component.I
Index
1
Element
Name
Ygse
Qualifier
Component.J
Index
2
Element
Name
Zgse
Qualifier
Component.K
Index
3
ValidMin
-50.0
ValidMax
50.0
FillValue
9999.0
Support
Qualifier
Vector
SupportQuantity
Positional
Parameter #7
Name
Spacecraft Position Y-component GSM
ParameterKey
ygsm
Description

Spacecraft position Y-component in GSM coordinates

Units
Re
UnitsConversion
6.378e6>m
CoordinateSystem
CoordinateRepresentation
Cartesian
CoordinateSystemName
GSM
ValidMin
-50.0
ValidMax
50.0
FillValue
9999.0
Support
Qualifier
Component.J
SupportQuantity
Positional
Parameter #8
Name
Spacecraft Position Z-component GSM
ParameterKey
zgsm
Description

Spacecraft position Z-component in GSM coordinates

Units
Re
UnitsConversion
6.378e6>m
CoordinateSystem
CoordinateRepresentation
Cartesian
CoordinateSystemName
GSM
ValidMin
-50.0
ValidMax
50.0
FillValue
9999.0
Support
Qualifier
Component.K
SupportQuantity
Positional
Parameter #9
Name
V fit
ParameterKey
V_fit
Description

(Better, from fits) Ion Flow Velocity (aberration corrected)

Caveats
Effects due to the orbital motion of Earth are removed from the better (fits) parameters, but not from the moment parameters.
Units
km/s
UnitsConversion
1e3>m/s
CoordinateSystem
CoordinateRepresentation
Spherical
CoordinateSystemName
GSE
ValidMin
100.0
ValidMax
3000.0
FillValue
9999.0
Particle
ParticleType
Proton
ParticleType
Ion
Qualifier
Fit
Qualifier
Magnitude
ParticleQuantity
FlowVelocity
Parameter #10
Name
V moments
ParameterKey
V_mom
Description

(From moments) Proton Flow Velocity (no aberration
correction)

Caveats
Effects due to the orbital motion of Earth are removed from the better (fits) parameters, but not from the moment parameters.
Units
km/s
UnitsConversion
1e3>m/s
CoordinateSystem
CoordinateRepresentation
Spherical
CoordinateSystemName
GSE
ValidMin
100.0
ValidMax
3000.0
FillValue
9999.0
Particle
ParticleType
Proton
ParticleType
Ion
Qualifier
Moment
Qualifier
Magnitude
ParticleQuantity
FlowVelocity
Parameter #11
Name
Proton V thermal fit
ParameterKey
protonV_thermal_fit
Description

(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.

Caveats
Effects due to the orbital motion of Earth are removed from the better (fits) parameters, but not from the moment parameters.
Units
km/s
UnitsConversion
1e3>m/s
ValidMin
1.0
ValidMax
500.0
FillValue
9999.0
Particle
ParticleType
Proton
ParticleType
Ion
Qualifier
Fit
Qualifier
Scalar
ParticleQuantity
ThermalSpeed
Parameter #12
Name
Proton V thermal moments
ParameterKey
protonV_thermal_mom
Description

(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.

Caveats
Effects due to the orbital motion of Earth are removed from the better (fits) parameters, but not from the moment parameters. This is probably the most inaccurate moment parameter, since moments tend to underestimate the temperature in cold distributions.
Units
km/s
UnitsConversion
1e3>m/s
ValidMin
1.0
ValidMax
500.0
FillValue
9999.0
Particle
ParticleType
Proton
ParticleType
Ion
Qualifier
Moment
Qualifier
Scalar
ParticleQuantity
ThermalSpeed
Parameter #13
Name
Proton density fit
ParameterKey
proton_density_fit
Description

(Better, from fits) Proton number density

Units
cm^-3
UnitsConversion
1e6>m^-3
ValidMin
0.0
ValidMax
100.0
FillValue
9999.0
Particle
ParticleType
Proton
ParticleType
Ion
Qualifier
Fit
Qualifier
Scalar
ParticleQuantity
NumberDensity
Parameter #14
Name
Proton density moments
ParameterKey
proton_density_mom
Description

(From moments) Proton number density

Units
cm^-3
UnitsConversion
1e6>m^-3
ValidMin
0.0
ValidMax
100.0
FillValue
9999.0
Particle
ParticleType
Proton
ParticleType
Ion
Qualifier
Moment
Qualifier
Scalar
ParticleQuantity
NumberDensity
Parameter #15
Name
E/W flow angle best
ParameterKey
EW_flowangle_best
Description

(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.

Caveats
Effects due to the orbital motion of Earth are removed from the better (fits) parameters, but not from the moment parameters.
Units
deg
CoordinateSystem
CoordinateRepresentation
Spherical
CoordinateSystemName
GSE
ValidMin
-45.0
ValidMax
45.0
FillValue
9999.0
Particle
ParticleType
Proton
ParticleType
Ion
Qualifier
Fit
Qualifier
DirectionAngle.AzimuthAngle
ParticleQuantity
FlowVelocity
Parameter #16
Name
E/W flow angle moments
ParameterKey
EW_flowangle_mom
Description

(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.

Caveats
Effects due to the orbital motion of Earth are removed from the better (fits) parameters, but not from the moment parameters.
Units
deg
CoordinateSystem
CoordinateRepresentation
Spherical
CoordinateSystemName
GSE
ValidMin
-45.0
ValidMax
45.0
FillValue
9999.0
Particle
ParticleType
Proton
ParticleType
Ion
Qualifier
Moment
Qualifier
DirectionAngle.AzimuthAngle
ParticleQuantity
FlowVelocity
Parameter #17
Name
Flow elevation threshsp
ParameterKey
Flow_elevation_threshsp
Description

(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.

Caveats
Effects due to the orbital motion of Earth are removed from the better (fits) parameters, but not from the moment parameters.
Units
deg
CoordinateSystem
CoordinateRepresentation
Spherical
CoordinateSystemName
GSE
ValidMin
-45.0
ValidMax
45.0
FillValue
9999.0
Particle
ParticleType
Proton
ParticleType
Ion
Qualifier
Fit
Qualifier
DirectionAngle.ElevationAngle
ParticleQuantity
FlowVelocity
Parameter #18
Name
Flow elevation thresh
ParameterKey
Flow_elevation_thresh
Description

(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.

Caveats
Effects due to the orbital motion of Earth are removed from the better (fits) parameters, but not from the moment parameters.
Units
deg
CoordinateSystem
CoordinateRepresentation
Spherical
CoordinateSystemName
GSE
ValidMin
-45.0
ValidMax
45.0
FillValue
9999.0
Particle
ParticleType
Proton
ParticleType
Ion
Qualifier
Moment
Qualifier
DirectionAngle.ElevationAngle
ParticleQuantity
FlowVelocity