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Title: Characteristic of hot plasma in the Jovian magnetosphere: Results from the Voyager spacecraft

Abstract

The low-energy charged particle (LECP) experiment on the Voyager 1 and 2 spacecraft made measurements of the intensity, energy spectra, angular distributions and composition of ions (30 keV< or approx. =E< or approx. = 150 MeV) and the electrons (14 keV< or approx. =E< or approx. =10 MeV) during encounters with the Jovian magnetosphere in 1979. Detailed analysis of the multicomponent (H, He, O, S) low-energy (approx.30 keV to approx.4 MeV) ion population reveals the Jovian environment to be dominated by magnetospheric ions to distances > or approx. =200 R/sub J/ upstream and > or approx. =350 R/sub J/ downstream from the planet. Inside the magnetosphere, ions move generally in the sense of corotation to the dayside magnetopause, and on the nightside to distances of approx.130--150 R/sub J/, beyond this distance, but inside the magnetopause, ion flow abruptly changes to an antisunward, antiJupiter direction and continues to large (>350 R/sub J/) radial distances outside the magnetosphere. The ion particle spectrum is characterized by a nonthermal power law (E/sup -gamma/) component for E> or approx. =200 keV, and a convected Maxwellian for E< or approx. =200 with characteristic temperatures (kT) of approx.20--45 keV. Temperature maxima generally coincide with crossings of themore » Jovian plasma sheet, while at higher energies spectra become softer at the equator. The ion spectra and composition are affected strongly by convective flows in all parts of the magnetosphere. By using the observed spectra and angular distributions, density and pressure profiles are produced for ions measured above the lowest LECP detector threshold (E> or approx. =30 keV) and are compared with reported ambient total electron densities and magnetic field pressures. The particle pressures are found to be comparable to magnetic field pressures to at least approx.10 R/sub J/, i.e., Jovian magnetosphere dynamics are determined by pressure variations in a high ..beta.. plasma.« less

Authors:
; ; ; ; ; ; ;
Publication Date:
Research Org.:
The John Hopkins Univ., Laurel, Maryland
OSTI Identifier:
5567124
Resource Type:
Journal Article
Journal Name:
J. Geophys. Res.; (United States)
Additional Journal Information:
Journal Volume: 86:A10
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; JUPITER PLANET; PLANETARY MAGNETOSPHERES; HOT PLASMA; IONIC COMPOSITION; VOYAGER SPACE PROBES; ATMOSPHERES; PLANETARY ATMOSPHERES; PLANETS; PLASMA; SPACE VEHICLES; VEHICLES; 640107* - Astrophysics & Cosmology- Planetary Phenomena

Citation Formats

Krimgis, S M, Carbary, J F, Keath, E P, Bostrom, C O, Axford, W I, Gloeckler, G, Lanzerotti, L J, and Armstrong, T P. Characteristic of hot plasma in the Jovian magnetosphere: Results from the Voyager spacecraft. United States: N. p., 1981. Web. doi:10.1029/JA086iA10p08227.
Krimgis, S M, Carbary, J F, Keath, E P, Bostrom, C O, Axford, W I, Gloeckler, G, Lanzerotti, L J, & Armstrong, T P. Characteristic of hot plasma in the Jovian magnetosphere: Results from the Voyager spacecraft. United States. doi:10.1029/JA086iA10p08227.
Krimgis, S M, Carbary, J F, Keath, E P, Bostrom, C O, Axford, W I, Gloeckler, G, Lanzerotti, L J, and Armstrong, T P. Wed . "Characteristic of hot plasma in the Jovian magnetosphere: Results from the Voyager spacecraft". United States. doi:10.1029/JA086iA10p08227.
@article{osti_5567124,
title = {Characteristic of hot plasma in the Jovian magnetosphere: Results from the Voyager spacecraft},
author = {Krimgis, S M and Carbary, J F and Keath, E P and Bostrom, C O and Axford, W I and Gloeckler, G and Lanzerotti, L J and Armstrong, T P},
abstractNote = {The low-energy charged particle (LECP) experiment on the Voyager 1 and 2 spacecraft made measurements of the intensity, energy spectra, angular distributions and composition of ions (30 keV< or approx. =E< or approx. = 150 MeV) and the electrons (14 keV< or approx. =E< or approx. =10 MeV) during encounters with the Jovian magnetosphere in 1979. Detailed analysis of the multicomponent (H, He, O, S) low-energy (approx.30 keV to approx.4 MeV) ion population reveals the Jovian environment to be dominated by magnetospheric ions to distances > or approx. =200 R/sub J/ upstream and > or approx. =350 R/sub J/ downstream from the planet. Inside the magnetosphere, ions move generally in the sense of corotation to the dayside magnetopause, and on the nightside to distances of approx.130--150 R/sub J/, beyond this distance, but inside the magnetopause, ion flow abruptly changes to an antisunward, antiJupiter direction and continues to large (>350 R/sub J/) radial distances outside the magnetosphere. The ion particle spectrum is characterized by a nonthermal power law (E/sup -gamma/) component for E> or approx. =200 keV, and a convected Maxwellian for E< or approx. =200 with characteristic temperatures (kT) of approx.20--45 keV. Temperature maxima generally coincide with crossings of the Jovian plasma sheet, while at higher energies spectra become softer at the equator. The ion spectra and composition are affected strongly by convective flows in all parts of the magnetosphere. By using the observed spectra and angular distributions, density and pressure profiles are produced for ions measured above the lowest LECP detector threshold (E> or approx. =30 keV) and are compared with reported ambient total electron densities and magnetic field pressures. The particle pressures are found to be comparable to magnetic field pressures to at least approx.10 R/sub J/, i.e., Jovian magnetosphere dynamics are determined by pressure variations in a high ..beta.. plasma.},
doi = {10.1029/JA086iA10p08227},
journal = {J. Geophys. Res.; (United States)},
number = ,
volume = 86:A10,
place = {United States},
year = {1981},
month = {9}
}