The Hot Plasma Environment at Jupiter: Ulysses Results
L. J. Lanzerotti 1,
T. P. Armstrong 2,
R. E. Gold 3,
K. A. Anderson 4,
S. M. Krimigis 3,
R. P. Lin 4,
M. Pick 5,
E. C. Roelof 3,
E. T. Sarris 6,
G. M. Simnett 7,
C. G. Maclennan 1,
H. T. Choo 2, and
S. J. Tappin 7
1 AT&T Bell Laboratories, Murray Hill, NJ 07974
2 Department of Physics, University of Kansas, Lawrence, KS 66045
3 The Johns Hopkins University/Applied Physics Laboratory, Laurel, MD 20723
4 Space Sciences Laboratory, University of California, Berkeley, CA 94720
5 Observatoire de Paris, 92195 Meudon Cedex, France
6 University of Thrace, Xanthi 67100, Greece
7 Department of Space Research, University of Birmingham, Birmingham B15 2TT, United Kingdom
Measurements of the hot plasma environment during the Ulysses flyby of Jupiter have revealed several new discoveries related to this large rotating astrophysical system. The Jovian magnetosphere was found by Ulysses to be very extended, with the day-side magnetopause located at 
105 Jupiter radii. The heavy ion (sulfur, oxygen, and sodium) population in the day-side magnetosphere increased sharply at 86 Jupiter radii. This is somewhat more extended than the "inner" magnetosphere boundary region identified by the Voyager hot plasma measurements. In the day-side magnetosphere, the ion fluxes have the anisotropy direction expected for corotation with the planet, with the magnitude of the anisotropy increasing when the spacecraft becomes more immersed in the hot plasma sheet. The relative abundances of sulfur, oxygen, and sodium to helium decreased somewhat with decreasing radial distance from the planet on the day-side, which suggests that the abundances of the Jupiter-derived species are dependent on latitude. In the dusk-side, high-latitude region, intense fluxes of counter-streaming ions and electrons were discovered from the edge of the plasma sheet to the dusk-side magnetopause. These beams of electrons and ions were found to be very tightly aligned with the magnetic field and to be superimposed on a time- and space-variable isotropic hot plasma background. The currents carried by the measured hot plasma particles are typically 1.6 x 10-4 microamperes per square meter or 8 x 105 amperes per squared Jupiter radius throughout the high-latitude magnetosphere volume. It is likely that the intense particle beams discovered at high Jovian latitudes produce auroras in the polar caps of the planet.
Submitted on June 1, 1992
Accepted on August 7, 1992
