PDS_VERSION_ID = PDS3
RECORD_TYPE = STREAM
OBJECT = TEXT
PUBLICATION_DATE = 1998-05-01
NOTE = "DATASET.TXT contains the data set description."
END_OBJECT = TEXT
END
Data Set Summary
================
Data Set ID: VG1-J-PLS-5-SUMM-ION-MOM-96.0SEC-V1.1
Instrument: PLS
Instrument P.I.: John D. Richardson
Data Supplier: John D. Richardson
Data sampling rate: 96 seconds
Data Set Start time: 1979-03-01T12:04:12.474Z
Data Set Stop time: 1979-03-05T16:45:54.608Z
Record format
-------------
These files can be read according to the FORTRAN format statement:
'(a24,1x,1pe9.2)'
where 'a24' is the time stamp in PDS format: yyyy-mm-ddThh:mm:ss.sssZ.
The individual elements of the time field can be read according to the
statement:
'(i4,4(1x,i2),1x,f6.3,1x)' year, month, day, hour, minute, seconds.
Thus a record may alternatively be read according to the format:
'(i4,4(1x,i2),1x,f6.3,2x,1pe9.2)'
Data column descriptions
------------------------
time a24 time in the format yyyy-mm-ddThh:mm:ss.sssZ
ion_mden 1pe9.2 total ion moment in units of counts/cm^3
Missing data flag value
-----------------------
Any data column whose value is -9.99e+10 is a missing data value.
Data Description
================
Version 1.1
-----------
This version 1.1 data set replaces the version 1.0 data set
(DATA_SET_ID = VG1-J-PLS-5-ION-MOM-96.0SEC) previously
archived with the PDS.
Data Set Description
--------------------
This data set contains the best estimates of the total ion
density at Jupiter during the Voyager 1 encounter in the PLS
voltage range (10-5950 eV/Q). It is calculated using the method
of [MCNUTTETAL1981] 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 before 1979 63
1300, after this the larger of the high and low resolution mode
densities in a 96 sec period is used since the L-mode spectra
often are saturated. 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
[MCNUTTETAL1981] 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. An overview
of the data in this data set can be found in [MCNUTTETAL1981]
and a complete instrument description can be found in
[BRIDGEETAL1977].
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 : EV
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 : VG1
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 : VG1-PLS
Software : MOMANAL
Product Data Set ID : VG1-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
Confidence Level Overview
-------------------------
This data set provides an estimate of the positive ion charge
density. Several assumption are made to simplify the analysis;
these 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 [MCNUTTETAL1981] 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.