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Science 29 January 1982:
Vol. 215. no. 4532, pp. 571 - 577
DOI: 10.1126/science.215.4532.571

Articles

Low-Energy Hot Plasma and Particles in Saturn's Magnetosphere

S. M. KRIMIGIS 1, T. P. ARMSTRONG 2, W. I. AXFORD 3, C. O. BOSTROM 4, G. GLOECKLER 5, E. P. KEATH 6, L. J. LANZEROTTI 7, J. F. CARBARY 6, D. C. HAMILTON 8, and E. C. ROELOF 6

1 Applied Physics Laboratory, Johns Hopkins University, Laurel, Maryland 20707
2 Department of Physics, University of Kansas, Lawrence 66044
3 Max-Planck Institute for Aeronomy, D-3411 Katlenburg-Lindau 3, West Germany
4 Applied Physics Laboratory, John Hopkins University
5 Department of Physics and Astronomy, University of Maryland, College Park
6 Applied Physics Laboratory, Johns Hopkins University
7 Bell Laboratories, Murray Hill, New Jersey 07974
8 Department of Physics and Astronomy, University of Maryland

The low-energy charged particle instrument on Voyager 2 measured low-energy electrons and ions (energies gsim 22 and gsim 28 kiloelectron volts, respectively) in Saturn's magnetosphere. The magnetosphere structure and particle population were modified from those observed during the Voyager 1 encounter in November 1980 but in a manner consistent with the same global morphology. Major results include the following. (i) A region containing an extremely hot ( sim 30 to 50 kiloelectron volts) plasma was identified and extends from the orbit of Tethys outward past the orbit of Rhea. (ii) The low-energy ion mantle found by Voyager 1 to extend sim 7 Saturn radii inside the dayside magnetosphere was again observed on Voyager 2, but it was considerably hotter ( sim 30 kiloelectron volts), and there was an indication of a cooler ( < 20 kiloelectron volts) ion mantle on the nightside. (iii) At energies gsim 200 kiloelectron volts per nucleon, H1, H2, and H3 (molecular hydrogen), helium, carbon, and oxygen are important constituents in the Saturnian magnetosphere. The presence of both H2 and H3 suggests that the Saturnian ionosphere feeds plasma into the magnetosphere, but relative abundances of the energetic helium, carbon, and oxygen ions are consistent with a solar wind origin. (iv) Low-energy ( sim 22 to sim 60 kiloelectron volts) electron flux enhancements observed between the L shells of Rhea and Tethys by Voyager 2 on the dayside were absent during the Voyager 1 encounter. (v) Persistent asymmetric pitch-angle distributions of electrons of 60 to 200 kiloelectron volts occur in the outer magnetosphere in conjunction with the hot ion plasma torus. (vi) The spacecraft passed within sim 1.1° in longitude of the Tethys flux tube outbound and observed it to be empty of energetic ions and electrons; the microsignature of Enceladus inbound was also observed. (vii) There are large fluxes of electrons of sim 1.5 million electron volts and smaller fluxes of electrons of sim 10 million electron volts and of protons gsim 54 million electron volts inside the orbits of Enceladus and Mimas; all were sharply peaked perpendicular to the local magnetic field. (viii) In general, observed satellite absorption signatures were not located at positions predicted on the basis of dipole magnetic field models.

Submitted on November 10, 1981


THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES:
Dynamics of Saturn's Magnetosphere from MIMI During Cassini's Orbital Insertion.
S. M. Krimigis, D. G. Mitchell, D. C. Hamilton, N. Krupp, S. Livi, E. C. Roelof, J. Dandouras, T. P. Armstrong, B. H. Mauk, C. Paranicas, et al. (2005)
Science 307, 1270-1273
   Abstract »    Full Text »    PDF »
Hot Plasma and Energetic Particles in Neptune's Magnetosphere.
S. M. Krimigis, T. P. Armstrong, W. I. Axford, C. O. Bostrom, A. F. Cheng, G. Gloeckler, D. C. Hamilton, E. P. Keath, L. J. Lanzerotti, B. H. Mauk, et al. (1989)
Science 246, 1483-1489
   Abstract »    PDF »
Voyager 2 Plasma Wave Observations at Saturn.
F. L. SCARF, D. A. GURNETT, W. S. KURTH, and R. L. POYNTER (1982)
Science 215, 587-594
   Abstract »    PDF »



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