A CONVECTED KAPPA DISTRIBUTION MODEL FOR HOT IONS IN THE JOVIAN MAGNETODISC

Hot ion angular anisotropies measured by the Low Energy Charged Particle (LECP) instrument during the Voyager 2 encounter with the Jovian dayside outer magnetosphere (60-30 R(J)) have been fitted to a 2 species convected kappa-distribution function using a non-linear least squares technique. The resulting parameters are well constrained by the data. The heavy ion species was assumed to be either sulfur or oxygen of unknown charge. The light species was assumed to be protons. The bulk flow speeds deduced from the model were found, contrary to some theories, to increase with increasing radial distance from Jupiter within the radial region addressed, remaining a substantial fraction (approximately 0.6) of the rigid corotation speed. Agreement with the averaged Voyager Plasma Science (PLS) results was obtained near 30 R(J). The core Maxwellian temperature of the heavy ion distribution functions (approximately 30-100 keV) increased with increasing radial distance, following the trend anticipated from the corotation pickup of heavy ions. The proton temperature (approximately 20 keV) remained nearly constant.