2.3.2 spase://NASA/NumericalData/IMP8/PLS/PT01M IMP 8 MIT Full Resolution Definitive Interplanetary Plasma Data IMP 8 Solar Wind Plasma Faraday Cup Data 2021-04-27T15:38:11Z 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. For papers and presentations using these data, please acknowledge the MIT Space Plasma Physics Group and the path through which you accessed the data. spase://SMWG/Person/Alan.J.Lazarus PrincipalInvestigator spase://SMWG/Person/John.D.Richardson TeamMember Readme file at SPDF https://spdf.gsfc.nasa.gov/pub/data/imp/imp8/plasma_mit/sw_msheath_min/00readme.txt Text created by MIT IMP8 plasma team spase://VMO/NumericalData/IMP8/PLS/PT01M spase://VSPO/NumericalData/IMP8/PLS/PT01M spase://SMWG/Repository/NASA/GSFC/SPDF Online Open FTPS from SPDF (not with most browsers) ftps://spdf.gsfc.nasa.gov/pub/data/imp/imp8/plasma_mit/ HTTPS from SPDF https://spdf.gsfc.nasa.gov/pub/data/imp/imp8/plasma_mit/ In CDF via HTTP from SPDF CDF spase://SMWG/Repository/NASA/GSFC/SPDF Online Open CDAWeb https://cdaweb.gsfc.nasa.gov/cgi-bin/eval2.cgi?dataset=I8_H0_MITPLASMA&index=sp_phys I8_H0_MITPLASMA With subset, plot and list functionalities FTPBrowser https://omniweb.sci.gsfc.nasa.gov/ftpbrowser/imp_mit_min.html With subset, plot and list functionalities Text spase://SMWG/Repository/NASA/GSFC/SPDF Online Open CDAWeb HAPI Server https://cdaweb.gsfc.nasa.gov/hapi I8_H0_MITPLASMA Web Service to this product using the HAPI interface. CSV Calibrated v01 spase://SMWG/Instrument/IMP8/PLS ThermalPlasma 1973-10-31T20:10:26 2006-07-26T17:10:34 PT01M Heliosphere.NearEarth Earth.Magnetosheath 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. Time Epoch Time 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. -1.0E31 Scalar Temporal Spacecraft Spacecraft Spacecraft flag (6/7/8 = IMP 6/7/8) 0 8 9 Other Decimal Year decimal_year Decimal year 1972.0 2020.0 100000.0 Scalar Temporal Region Region 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. 1 8 9 Other Operating mode mode 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. 1 8 9 Other Spacecraft Position GSE SC_Pos_GSE Spacecraft position in GSE coordinates Re 6.378e6>m Cartesian GSE 3 Xgse Component.I 1 Ygse Component.J 2 Zgse Component.K 3 -50.0 50.0 9999.0 Vector Positional Spacecraft Position Y-component GSM ygsm Spacecraft position Y-component in GSM coordinates Re 6.378e6>m Cartesian GSM -50.0 50.0 9999.0 Component.J Positional Spacecraft Position Z-component GSM zgsm Spacecraft position Z-component in GSM coordinates Re 6.378e6>m Cartesian GSM -50.0 50.0 9999.0 Component.K Positional V fit V_fit (Better, from fits) Ion Flow Velocity (aberration corrected) Effects due to the orbital motion of Earth are removed from the better (fits) parameters, but not from the moment parameters. km/s 1e3>m/s Spherical GSE 100.0 3000.0 9999.0 Proton Ion Fit Magnitude FlowVelocity V moments V_mom (From moments) Proton Flow Velocity (no aberration correction) Effects due to the orbital motion of Earth are removed from the better (fits) parameters, but not from the moment parameters. km/s 1e3>m/s Spherical GSE 100.0 3000.0 9999.0 Proton Ion Moment Magnitude FlowVelocity Proton V thermal fit protonV_thermal_fit (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. Effects due to the orbital motion of Earth are removed from the better (fits) parameters, but not from the moment parameters. km/s 1e3>m/s 1.0 500.0 9999.0 Proton Ion Fit Scalar ThermalSpeed Proton V thermal moments protonV_thermal_mom (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. 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. km/s 1e3>m/s 1.0 500.0 9999.0 Proton Ion Moment Scalar ThermalSpeed Proton density fit proton_density_fit (Better, from fits) Proton number density cm^-3 1e6>m^-3 0.0 100.0 9999.0 Proton Ion Fit Scalar NumberDensity Proton density moments proton_density_mom (From moments) Proton number density cm^-3 1e6>m^-3 0.0 100.0 9999.0 Proton Ion Moment Scalar NumberDensity E/W flow angle best EW_flowangle_best (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. Effects due to the orbital motion of Earth are removed from the better (fits) parameters, but not from the moment parameters. deg Spherical GSE -45.0 45.0 9999.0 Proton Ion Fit DirectionAngle.AzimuthAngle FlowVelocity E/W flow angle moments EW_flowangle_mom (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. Effects due to the orbital motion of Earth are removed from the better (fits) parameters, but not from the moment parameters. deg Spherical GSE -45.0 45.0 9999.0 Proton Ion Moment DirectionAngle.AzimuthAngle FlowVelocity Flow elevation threshsp Flow_elevation_threshsp (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. Effects due to the orbital motion of Earth are removed from the better (fits) parameters, but not from the moment parameters. deg Spherical GSE -45.0 45.0 9999.0 Proton Ion Fit DirectionAngle.ElevationAngle FlowVelocity Flow elevation thresh Flow_elevation_thresh (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. Effects due to the orbital motion of Earth are removed from the better (fits) parameters, but not from the moment parameters. deg Spherical GSE -45.0 45.0 9999.0 Proton Ion Moment DirectionAngle.ElevationAngle FlowVelocity