ON THE FORMATION OF IO-INDUCED ACCELERATION REGIONS RELATED TO JOVIANAURORA

By means of 3D resistive MHD simulations ewe present an effective mech anism to accelerate charged particles which may contribute to the Jovi an aur-oral luminosity. We restrict ourselves to the So-induced part, the so-called Io footprint. We apply the present knowledge about the t errestrial aurora to Jupiter and perform in a first step global simula tions of the Jovian magnetosphere in order to investigate the generati on of a field-aligned current system by Io with particular stress on t he influence of mass loading effects, The MHD modes excited by this in teraction transport the velocity shear and magnetic perturbations into the Jovian ionosphere, thereby establishing a current system similar to the Birkeland currents in the Earth's magnetosphere-ionosphere syst em. In a second step we perform local simulations of the Jovian magnet osphere-ionosphere system. In the considered latitudes in consequence of the velocity shear the current density is expected to rise up to su percritical values exciting microinstabilities which lead to anomalous resistive instabilities which in their nonlinear evolution result in considerably enhanced parallel electric fields. Thus, a field-aligned potential can be built up in these resistive regions accelerating char ged particles to energies of several keV. (C) 1998 Elsevier Science Lt d. All rights reserved.