Energetic particles in the duskside Jovian Magnetosphere

The paper provides a detailed description of energetic ion measurements fro m the Energetic Particle Composition instrument (EPAC) and magnetic field m easurements from the dual-technique magnetometer on board Ulysses made in t he duskside Jovian magnetosphere after its Jupiter flyby on February 8, 199 2. The Ulysses spacecraft performed these in situ measurements on its outbo und trajectory passing through the local time sector between 2100 and 1830 from northern to relatively high southern latitudes. The outbound pass is d ivided into six different regions, which are differentiated by magnetic fie ld measurements and by the behavior of the particle intensities, ion spectr a, and composition, as well as ion anisotropies. At a distance of 21 R-J th e energy spectrum of 0.57-1.42 MeV protons suddenly becomes much softer, in dicative of a transition between a dipolar-like inner magnetosphere and the inner edge of the plasma sheet. The EPAC instrument observes a dramatic in crease in all particle intensities at distances around 50 R-J at southern m agnetic latitudes of 30 degrees S. The intensity levels are as high as thos e observed during the inbound equatorial plasma sheet crossings at comparab le distances. The increase is interpreted as a temporal phenomenon associat ed with a thickening of the plasma sheet. After the first magnetopause cros sings at distances near 80 R-J, EPAC measurements reveal signatures of magn etospheric particles existing in the magnetosheath which imply that the Jov ian magnetosphere is open. Following a change in the interplanetary magneti c field orientation, these particles are then no longer observed within the magnetosheath. A further puzzling particle observation along the Ulysses o utbound pass is the reentry into the magnetosphere between 115 and 124 R-J at 37 degrees southern magnetic latitude. It impressively shows the high va riability of the Jovian magnetosphere.