Metadata Updated: November 12, 2020

This data set gives the best available values for ion densities, temperatures, and velocities near Neptune derived from data obtained by the Voyager 2 plasma experiment. All parameters are obtained by fitting the observed spectra (current as a function of energy) with Maxwellian plasma distributions, using a non-linear least squares fitting routine to find the plasma parameters which, when coupled with the full instrument response, best simulate the data. The PLS instrument measures energy/charge, so composition is not uniquely determined but can be deduced in some cases by the separation of the observed current peaks in energy (assuming the plasma is co-moving). In the upstream solar wind protons are fit to the M-long data since high energy resolution is needed to obtain accurate plasma parameters. In the magnetosheath the ion flux so low that several L-long spectra (3-5) had to be averaged to increase the signal-to-noise ratio to a level at which the data could be reliably fit. These averaged spectra were fit using 2 proton maxwellians with the same velocity. The values given in the upstream magnetosheath are the total density and the density-weighted temperature. In both the upstream solar wind and magnetosheath full vector velocities, densities and temperatures are derived for each fit component. In the magnetosphere spectra do not contain enough information to obtain full velocity vectors, so flow is assumed to be purely azimuthal. In some cases the azimuthal velocity is a fit parameter, in some cases rigid corotation is assumed. In the 'outer' magnetosphere (L>5) two distinct current peaks appear in the spectra H+ and N+. In the inner magnetosphere the plasma is hot and the composition is ambiguous, although two superimposed Maxwellians are still required to fit the data. These spectra are fit using two compositions, one with H+ and N+ and the second with two H+ components. The N+ composition is preferred by the data provider. All fit values in the magnetosphere come with one sigma errors. It should be noted that no attempt has been made to account for the spacecraft potential, which is probably about -10 V in this region and will effect the density and velocity values. In the outbound magnetosheath and solar wind both moment and fit values are given for velocity, density, and thermal speed. The signal-to-noise ratio in the M-longs is very low, especially near the magnetopause, which can result in the analysis giving incorrect values. The L-long spectra have too low an energy resolution to permit accurate determinations parameters in many regions temperature and non-radial velocity components may be inaccurate.

Access & Use Information

Public: This dataset is intended for public access and use. License: No license information was provided. If this work was prepared by an officer or employee of the United States government as part of that person's official duties it is considered a U.S. Government Work.

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Metadata Created Date November 12, 2020
Metadata Updated Date November 12, 2020
Data Update Frequency irregular

Metadata Source

Harvested from NASA Data.json

Additional Metadata

Resource Type Dataset
Metadata Created Date November 12, 2020
Metadata Updated Date November 12, 2020
Publisher National Aeronautics and Space Administration
Unique Identifier Unknown
Identifier urn:nasa:pds:context_pds3:data_set:data_set.vg2-n-pls-5-rdr-ionmagsphere-48sec-v1.0
Data First Published 2018-06-26
Data Last Modified 2020-01-29
Category Earth Science
Public Access Level public
Data Update Frequency irregular
Bureau Code 026:00
Metadata Context
Metadata Catalog ID
Schema Version
Catalog Describedby
Homepage URL
Program Code 026:005
Related Documents
Source Datajson Identifier True
Source Hash 302666b382d9148bc26a9ef41a75d625b388b4e5
Source Schema Version 1.1

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