ULYSSES MEASUREMENTS OF ENERGETIC H-3 MOLECULES IN JUPITER MAGNETOSPHERE

The Voyager 2 measurements of energetic (approximately 1 MeV/nucleon) H-3 Molecules in Jupiter's magnetosphere provided strong evidence that the planet's ionosphere is an important plasma source in the Jovian e nvironment (Hamilton et al., 1980). During the Ulysses spacecraft enco unter with Jupiter in February 1992 the Heliosphere Instrument for Spe ctra, Composition, and Anisotropy at Low Energies (HI-SCALE) on this s atellite also detected significant fluxes of energetic H-3 molecules. These molecules were measured throughout the dayside inbound pass (rea r the plasma sheet) as well as during the outbound pass at high Jovian latitudes on the duskside. The spectral shapes of the energetic He-4 and the H-3 are found to be similar over the range approximately 0.6 - 1.6 MeV/nucleon, with a power law spectral slope of n approximately 3 . The abundance ratio R (=H-3/He-4) is found to be approximately 0.1 o ver this energy range for die inbound pass and to vary from approximat ely 0.2 at approximately 0.6 MeV/nucleon to approximately 0.1 at appro ximately 1.6 MeV/nucleon at duskside high latitudes. These observation s, especially those from high latitudes, confirm that the energetic mo lecules must be accelerated out of die Jovian topside ionosphere into the magnetosphere.