PDS3_DATA_SET_ID = VG1-J-PLS-5-SUMM-ELE-MOM-96.0SEC-V1.1 DATA_SET_NAME = VG1 JUP PLASMA DERIVED ELECTRON MOMENTS 96.0 SEC V1.1 START_TIME = 1979-03-01T12:27:43.435 STOP_TIME = 1979-03-07T11:59:03.738 ORIGINAL_DATA_SET_RELEASE_DATE = 1998-05-01 PRODUCER_FULL_NAME = JOHN D. RICHARDSON REFERENCES: Bridge, H.S., J.W. Belcher, R.J. Butler, A.J. Lazarus, A.M. Mavretic, J.D. Sullivan, G.L. Siscoe, and V.M. Vasyliunas, The Plasma Experiment on the 1977 Voyager Mission, Space Sci. Rev., Vol. 21, p. 259, 1977. Bridge, H.S., J.W. Belcher, A.J. Lazarus, J.D. Sullivan, R.L. McNutt, F. Bagenal, J.D. Scudder, E.C. Sittler, G.L. Siscoe, V.M. Vasyliunas, C.K. Goertz, and C.M. Yeates, Plasma Observations Near Jupiter: Initial Results from Voyager 1, Science, Vol. 204, p. 987, 1979. Scudder, J.D., E.C. Sittler, and H.S. Bridge, Survey of the Plasma Electron Environment of Jupiter: A View from Voyager, J. Geophys. Res., Vol. 86, p. 8157, 1981. Sittler, E.C., Jr., and D.F. Strobel, Io Plasma Torus Electrons: Voyager 1, J. Geophys. Res., Vol. 92, p. 5741, 1987. DATA_SET_DESCRIPTION Data Set Overview ================= Version 1.1 ----------- This version 1.1 data set replaces the version 1.0 data set (DATA_SET_ID = VG1-J-PLS/PRA-5-ELE-MOM-96.0SEC) previously archived with the PDS. Data Set Description -------------------- This data set contains derived values of the electron density and moment temperature at Jupiter during the Voyager 1 encounter in the PLS voltage range (10-5950 eV/q). Adjacent low and high energy electron measurements are combined to form a composite spectra which is used for the moment calculation. The moment calculations are performed as described in [SCUDDERETAL1981]. These assume isotropic distributions and correct for positive spacecraft charge when applicable and interpolate electron spectra below the 10 eV instrument threshold before performing the integration over velocity. On day 64 from 415-1830 negative charging of the spacecraft renders electron moment densities unreliable. Therefore, the PLS ion densities were used to derive electron densities from 0415-1400 assuming charge neutrality and from 1830-1940 using a model based on inbound plasma parameters. PRA densities were used to derive electron densities from 1400 to 1830. Electron temperatures derived from PLS electron data are used except inside L=5.4, where T[E] was set equal to T[I] and should be considered an upper limit. The data used from 415-1830 on day 64 are described in [SITTLER&STROBEL1987]. Data format: column 1 is time (yyyy-mm-ddThh:mm:ss.sssZ), column 2 is the moment density in cm^-3, column 3 the temperature in eV. Each row has format (a24, 2(1x,1pe9.2)). Values of -9.99e+10 indicate that the parameter could not be obtained from the data using the standard analysis technique. Additional information about this data set and the instrument which produced it can be found elsewhere in this catalog. An overview of the data in this data set can be found in [SCUDDERETAL1981] and [SITTLER&STROBEL1987] and a complete instrument description can be found in [BRIDGEETAL1977]. Processing Level Id : 5 Software Flag : Y Processing Start Time : UNK Processing Stop Time : UNK Parameters ========== Sampling Parameter Name : TIME Data Set Parameter Name : ELECTRON DENSITY Sampling Parameter Resolution : 96.000000 Sampling Parameter Interval : 96.000000 Minimum Available Sampling Int : 96.000000 Data Set Parameter Unit : CM-3 Sampling Parameter Unit : SECOND A derived parameter equaling the number of electrons per unit volume over a specified range of electron energy. Different forms of electron density are distinguished by method of derivation (Maxwellian fit, method of moments) or by some selection criteria (ie., hot electron and cold electron density). In general, if more than one electron component is analyzed, either by moment or fit, a total density will be provided which is the sum of the electron densities. If the electrons do not have a Maxwellian distribution the actual distribution can be represented as the sum of several Maxwellians, in which case the density of each Maxwellian is given. Sampling Parameter Name : TIME Data Set Parameter Name : ELECTRON TEMPERATURE Sampling Parameter Resolution : 96.000000 Sampling Parameter Interval : 96.000000 Minimum Available Sampling Int : 96.000000 Data Set Parameter Unit : EV Sampling Parameter Unit : SECOND A derived parameter giving an indication of the mean energy/electron, assuming the shape of the electron energy derived spectrum to be Maxwellian. Given that the electron energy spectrum is not exactly Maxwellian, the electron temperature can be defined integrally (whereby the mean energy obtained by integrating under the actual electron energy spectrum is set equal to the integral under a Maxwellian, where the temperature is a free parameter for which to solve), or differentially (whereby the slopes of the actually electron energy spectrum at various energies are matched to the slopes of a corresponding Maxwellian). The temperature parameter is often qualified with a range of applicable energies. Temperatures can be angularly anisotropic. If the electrons do not have a Maxwellian distribution the actual distribution can be represented as the sum of several Maxwellians, each with a separate temperature. Source Instrument Parameters ============================ Instrument Host ID : VG1 Data Set Parameter Name : ELECTRON DENSITY Instrument Parameter Name : ELECTRON RATE ELECTRON CURRENT Important Instrument Parameters : 1 (for both inst. parameters) Instrument Host ID : VG1 Data Set Parameter Name : ELECTRON TEMPERATURE Instrument Parameter Name : ELECTRON RATE ELECTRON CURRENT Important Instrument Parameters : 1 (for both inst. parameters) Processing ========== Processing History ------------------ Source Data Set ID : VG1-PLS Software : UNK Product Data Set ID : VG1-J-PLS/PRA-5-ELE-MOM-96.0SEC Data Coverage ============= Filename Records Start Stop ------------------------------------------------------------------- T790301 5380 1979-03-01T12:27:43.435Z 1979-03-07T11:59:03.738Z CONFIDENCE_LEVEL_NOTE = Confidence Level Overview ========================= This data set provides the best estimate available of the total electron density in the PLS energy range (10-5950 eV). Four assumptions were made 1) secondary electrons escaping from the collector plate of the detector were neglected; 2) extrapolations were made to estimate the number of electrons outside the PLS energy range; 3) electrons were assumed to have isotropic distributions; 4) where the spacecraft potential was small the shape of the thermal electron spectra was used to estimate the charge and correct the derived densities. 1) Should result in an underestimate of the electron density by no more than 10% for electron temperature (T[E]) < 100 eV and no more than 30% for T[E] > 100 eV. 2) Gives uncertainties of at most 10%, and usually much smaller, for T[E] = 5-3000 eV which is the T[E] range measured in this region. 3) Should be an excellent assumption since isotropization times for electrons are fast, and since the electron thermal speed is always much greater than the plasma flow speed. 4) In regions where the spacecraft charge is positive (outside 10 R[J]) charging produces uncertainties of at most 10%. inside of ~10 R[J] the spacecraft potential is negative and electron densities are not reliable. From 0415 to 1940 on March 5 the ion charge density was used to estimate the electron density using the condition of charge neutrality. Uncertainties for the ion charge density in this region are less than 10%. From 1400-1830 electron densities derived from PRA densities are used; these have uncertainties of at most 20%. From 1830-1940 no direct measurement of electron density is available and 'predict densities' based on inbound ion measurements and a model of the plasma distribution are used. T[E] in all regions except between 1000 and 1350 is calculated from the PLS electron data and has uncertainties approximately equal to the density uncertainties. Between 1000 and 1350 T[E] is so far below the instrument threshold of 10 eV that no signal is seen; in this region te is set equal to the ion temperature observed at the same L shell and should be considered an upper limit. Missing Data Flag ================= Any column whose value is -9.99e+10 is a bad or missing data value.