Voyager 2 Plasma Science Experiment (PLS) Jupiter Data Bundle
Plasma Derived Ion Moments 96.0 Second Jupiter Data Description
PDS3_DATA_SET_ID = VG2-J-PLS-5-SUMM-ION-MOM-96.0SEC-V1.0
PDS3_DATA_SET_NAME = VG2 JUP PLS PLASMA DERIVED ION MOMENTS
96.0 SEC V1.1
START_TIME = 1979-07-04T12:02:47.821
STOP_TIME = 1979-07-10T11:59:35.443
ORIGINAL_DATA_SET_RELEASE_DATE = 1997-12-01
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, F. Bagenal, R.L.
McNutt, K.W. Ogilvie, J.D. Scudder, E.C. Sittler, V.M. Vasyliunas, and C.K.
Goertz, Plasma Observations Near Jupiter: Initial Results from Voyager 2,
Science, Vol. 206, p. 972, 1979.
McNutt, R.L., J.W. Belcher, and H.S. Bridge, Positive Ion Observations in the
Middle Magnetosphere of Jupiter, J. Geophys. Res., Vol. 86, p. 8319, 1981.
Collection Overview
=================
This collection contains the best estimates of the total ion
density from Voyager 2 at Jupiter in the PLS voltage range
(10-5950 eV/Q). It is calculated using the method of
[McNutt Et Al, 1981] which to first order consists of taking the
total measured current and dividing by the collector area and
plasma bulk velocity. This method is only accurate for high
mach number flows directly into the detector, and may result
in underestimates of the total density of a factor of 2 in the
outer magnetosphere. Thus absolute densities should be treated
with caution, but density variations in the data set can be
trusted. The low resolution mode density is used at all times
except day 190 2100-2200 when the larger of the high and low
resolution mode densities in a 96 sec period is used.
Corotation is assumed inside L=17.5, and a constant velocity
component of 200 km/s into the D cup is used outside of this.
These are the densities given in the [McNutt Et Al, 1981] paper
corrected by a factor of 1.209 (.9617) for densities obtained
from the side (main) sensor. This correction is due to a
better calculation of the effective area of the sensors. Data
format: column 1 is time (yyyy-mm-ddThh:mm:ss.sssZ), column 2
is the moment density in cm^-3. Each row has format (a24, 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.
Processing Level Id : 5
Software Flag : Y
Parameters
==========
Ion Density
-----------
Sampling Parameter Name : TIME
Data Set Parameter Name : ION 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 ions per unit
volume over a specified range of ion energy, energy/charge, or
energy/nucleon. Discrimination with regard to mass and or
charge state is necessary to obtain this quantity, however,
mass and charge state are often assumed due to instrument
limitations.
Many different forms of ion density are derived. Some are
distinguished by their composition (N+, proton, ion, etc.) or
their method of derivation (Maxwellian fit, method of
moments). In some cases, more than one type of density will be
provided in a single data set. In general, if more than one
ion species is analyzed, either by moment or fit, a total
density will be provided which is the sum of the ion
densities. If a plasma component does 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.
Source Instrument Parameters
============================
Instrument Host ID : VG2
Data Set Parameter Name : ION DENSITY
Instrument Parameter Name : ION RATE
ION CURRENT
PARTICLE MULTIPLE PARAMETERS
Important Instrument Parameters : 1 (for all parameters)
Processing
==========
Processing History
------------------
Source Data Set ID : VG2-PLS
Software : MOMANAL
Product Data Set ID : VG2-J-PLS-5-ION-MOM-96.0SEC
Software 'MOMANAL'
------------------
Software Name : MOMANAL
Software Type : PIN
Software Release Date : N/A
Node ID : N/A
Cognizant Engineer : N/A
Software Access Description : N/A
Data Coverage
=============
Filename Records Start Stop
-------------------------------------------------------------------
ION_MOM.TAB 5399 1979-07-04T12:02:47.821Z 1979-07-10T11:59:35.443Z
CONFIDENCE_LEVEL_NOTE
Confidence Level Overview
=========================
This data set provides an estimate of the positive ion charge
density. Several assumption/simplifications are made to
simplify the analysis which may affect the accuracy of the
results. High mach number flow is assumed; mach numbers of
2-3, which are reasonable lower limits for heavy ions, result
in 10-20% underestimates of the charge density. The analysis
assumes a unit response (ie., all particles in a cold beam
incident on the aperture of the experiment would be measured
at the collector). The actual response is documented in
[McNutt Et Al 1981] and can be as low as 70%. A velocity into the
detector must also be assumed; the velocity used is the
corotation velocity inside of 17.5 R[J] and 200 km/s outside
of this. This velocity profile is in accord with that measured
where velocity determinations are possible, but the use of
incorrect values give errors in the density which vary linearly
with errors in the velocity. Finally, only ions in the PLS
energy range (10-5950 eV/Q) are counted. The cumulative error
from all these effects is less than 10% in the solar wind, less
than a factor of two in the outer magnetosphere (r❯20 R[J]) and
less than 20-30% inside of this. Since the amplitude of each of
these effects varies slowly in time (distance), the relative
changes in density are good to a few percent in most cases.
Missing Data Flag
=================
Any column whose value is -9.99e+10 is a bad or missing data
value.
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