Hydrogen from Jupiter's Atmosphere in the Jovian Magnetosphere

U. Mall ¹, J. Geiss ¹, H. Balsiger ¹, G. Gloeckler ², A.B. Galvin ², B. Wilken ³

1. Physikalisches Institut, University of Bern, Sidlerstrasse 5, CH-3012 Bern, Switzerland

2. Department of Physics, University of Maryland, College Park, MD 20742, U.S.A.

3. Max-Planck-Institut für Aeronomie, 3411 Katlenburg-Lindau 3, Germany

The passage of Ulysses through Jupiter's magnetosphere presents a new opportunity to investigate the contribution to the Jovian magnetosphere of ions of atmospheric origin. A determination of the magnetospheric H⁺/He²⁺ flux ratio allows an estimate of the relative abundance of ionospheric material in the Jovian magnetosphere. We find the H⁺/He²⁺ flux ratio, measured in the energy/charge range between 0.65 and 60 keV/e, to steadily increase from a solar wind level of 25 at the magnetopause to a value of 700 at the point of closest approach, and then to steadily decrease whilst approaching the magnetopause on the outbound path. We conclude from this that: 1) there is a significant solar wind component throughout the outer and middle magnetosphere, and 2) a significant fraction of the protons in the middle magnetosphere are of non-solar origin.

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