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Detailed Reference Information |
Krimigis, S.M., Carbary, J.F., Keath, E.P., Armstrong, T.P., Lanzerotti, L.J. and Gloeckler, G. (1983). General Characteristics of Hot Plasma and Energetic Particles in the Saturnian Magnetosphere: Results from the Voyager Spacecraft. Journal of Geophysical Research 88: doi: 10.1029/JA080i011p08871. issn: 0148-0227. |
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The low energy charged particle (LECP) experiment on the Voyager 1 and 2 spacecraft made measurements of the intensity, energy spectra, and spatial distributions of ions (30 keV≲E≲150 MeV) and electrons (22 keV≲E≲20 MeV) during encounters with the Saturnian magnetosphere in November 1980 and August 1981, respectively. Detailed analysis of the data has revealed the following: (1) Energetic ions are present in the interplanetary medium both upstream (to ~ 200 RS) and off the dawn bow shock (to ~400 RS) of the magnetosphere, with maximum energies ~100 keV. (2) Low-energy (>22 keV) electrons are generally depleted inward of L~RS, while low-energy (>30 keV) ions are greatly enhanced in the same region. (3) The composition of low-energy ions is most likely domeinated by protons in the outer magnetosphere but is consistent with oxygen in the inner (L≲9) magnetosphere. (4) The ion spectrum is described well by the &kgr; distribution with characteristic temperatures kTH ranging from ~15 to ~55 keV; the hot plasma region is generally confined between the L shells of Tethys and Rhea but exhibits substantial variability. (5) The electron energy spectrum at L≲10 develops a secondary peak at E>200 keV that shifts to higher (~1 MeV) energies inside the orbits of Enceladus and Mimas, indicative of electron resonance interactions with the planetary satellites. (6) There is a noon-dawn asyummetry in ion and electron intensities with peak fluxes near the Rhea-Dione L shells at local morning: this is the region in local time where Saturn kilometric radiation is modulated by the presence of Dione. (7) The ion energy density (>30 keV) represents a significant fracction fo the field energy density in the outer magnetosphere of the planet (L>13 RS), with values of &Bgr; ranging from 0.1 up to ~4, when projected to the equator. (8) Comparison of electron and ion intensities measured by Voyager 1 and 2 in the inner L>13 RS) (L≲6) magnetosphere at common points in B, L space show that the radiation belts are substantially stable over periods ~9 months; both ion and electron intensities compared well with Pioneer 11 obsersvations in 1979. It is evident from the results that the inner satellites of Saturn play a dominant role in the determination of intensity and spectral features of energetic particles at L≲10. These aspects of the data are discussed in the context of proposed physical mechanisms expected to be operating within the magnetosphere of Saturn. |
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Publisher
American Geophysical Union 2000 Florida Avenue N.W. Washington, D.C. 20009-1277 USA 1-202-462-6900 1-202-328-0566 service@agu.org |
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