BULK FLOWS OF HOT PLASMA IN THE JOVIAN MAGNETOSPHERE - A MODEL OF ANISOTROPIC FLUXES OF ENERGETIC IONS

Since the Ulysses flyby of Jupiter in February 1992, a consistent pict ure of the bulk flows of hot plasma has yet to be formed. The present study reports a comprehensive analysis of energetic particle anisotrop ies from the Ulysses mission. We present an empirical model which sepa rates flow from gradient anisotropies. The model employs a multidimens ional minimization routine to fit simultaneously 13 free parameters us ing 98 measurements. The large number of independent measurements is p ossible because the Ulysses Heliosphere Instrument for Spectra, Compos ition, and Anisotropy at Low Energy (HI-SCALE) has nearly full angular coverage at high time resolution and moderately high angular resoluti on. The model uses the full energy range (similar to 50-3000 keV) of t he low-energy magnetic spectrometers and also the pure proton channels of the composition aperture on the instrument. We present flow result s during the inbound pass of Ulysses in which the radial velocity comp onent shows a persistent radial outflow. The azimuthal component is in the sense of planetary rotation but generally below rigid corotation, and the azimuthal velocity is greater near the plasma current sheet t han at higher magnetic latitudes. Outbound, the flows in the high-lati tude duskside magnetosphere inferred from the particle anisotropies in dicate, surprisingly, sunward flows opposite to planetary rotation. We find evidence of gradient anisotropies especially near the magnetosph eric current sheet on the dayside. We present a picture of the global magnetic field configuration and flows of hot plasma, consistent with our model results, dominated by subcorotation at low latitudes but by sunward flow at high latitudes.