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Science 29 January 1982:
Vol. 215. no. 4532, pp. 563 - 570
DOI: 10.1126/science.215.4532.563
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Articles

Plasma Observations Near Saturn: Initial Results from Voyager 2

H. S. BRIDGE 1, F. BAGENAL 1, J. W. BELCHER 1, A. J. LAZARUS 1, R. L. McNUTT 1, J. D. SULLIVAN 1, P. R. GAZIS 1, R. E. HARTLE 2, K. W. OGILVIE 3, J. D. SCUDDER 3, E. C. SITTLER 3, A. EVIATAR 4, G. L. SISCOE 4, C. K. GOERTZ 5, and V. M. VASYLIUNAS 6

1 Center for Space Research and Department of Physics, Massachusetts Institute of Technology, Cambridge 02139
2 Laboratory for Planetary Atmospheres, Goddard Space Flight Center, Greenbelt, Maryland 20771
3 Laboratory for Extraterrestrial Physics, Goddard Space Flight Center
4 Department of Atmospheric Sciences, University of California, Los Angeles 90024
5 Department of Physics and Astronomy, University of Iowa, Iowa City 52242
6 Max-Planck-Institut für Aeronomie, Katlenburg-Lindau, West Germany

Results of measurements of plasma electrons and poitive ions made during the Voyager 2 encounter with Saturn have been combined with measurements from Voyager 1 and Pioneer 11 to define more clearly the configuration of plasma in the Saturnian magnetosphere. The general morphology is well represented by four regions: (i) the shocked solar wind plasma in the magnetosheath, observed between about 30 and 22 Saturn radii (RS) near the noon meridian; (ii) a variable density region between sim 17 RS and the magnetopause; (iii) an extended thick plasma sheet between sim 17 and sim 7 RS symmetrical with respect to Saturn's equatorial plane and rotation axis; and (iv) an inner plasma torus that probably originates from local sources and extends inward from L ap 7 to less than L ap 2.7 (L is the magnetic shell parameter). In general, the heavy ions, probably O+, are more closely confined to the equatorial plane than H+, so that the ratio of heavy to light ions varies along the trajectory according to the distance of the spacecraft from the equatorial plane. The general configuration of the plasma sheet at Saturn found by Voyager 1 is confirmed, with some notable differences and additions. The "extended plasma sheet," observed between L ap 7 and L ap 15 by Voyager 1 is considerably thicker as observed by Voyager 2. Inward of L ap 4, the plasma sheet collapses to a thin region about the equatorial plane. At the ring plane crossing, L ap 2.7, the observations are consistent with a density of O+ of sim 100 per cubic centimeter, with a temperature of sim 10 electron volts. The location of the bow shock and magnetopause crossings were consistent with those previously observed. The entire magnetosphere was larger during the outbound passage of Voyager 2 than had been previously observed; however, a magnetosphere of this size or larger is expected sim 3 percent of the time.

Submitted on November 10, 1981


THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES:
Composition and Dynamics of Plasma in Saturn's Magnetosphere.
D. T. Young, J.-J. Berthelier, M. Blanc, J. L. Burch, S. Bolton, A. J. Coates, F. J. Crary, R. Goldstein, M. Grande, T. W. Hill, et al. (2005)
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Extreme Ultraviolet Observations from the Voyager 2 Encounter with Saturn.
B. R. SANDEL, D. E. SHEMANSKY, A. L. BROADFOOT, J. B. HOLBERG, G. R. SMITH, J. C. MCCONNELL, D. F. STROBEL, S. K. ATREYA, T. M. DONAHUE, H. W. MOOS, et al. (1982)
Science 215, 548-553
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Energetic Charged Particles in Saturn's Magnetosphere: Voyager 2 Results.
R. E. VOGT, D. L. CHENETTE, A. C. CUMMINGS, T. L. GARRARD, E. C. STONE, A. W. SCHARDT, J. H. TRAINOR, N. LAL, and F. B. McDONALD (1982)
Science 215, 577-582
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Planetary Radio Astronomy Observations from Voyager 2 Near Saturn.
J. W. WARWICK, D. R. EVANS, J. H. ROMIG, J. K. ALEXANDER, M. D. DESCH, M. L. KAISER, M. AUBIER, Y. LEBLANC, A. LECACHEUX, and B. M. PEDERSEN (1982)
Science 215, 582-587
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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
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