ON THE EXISTENCE OF SUPERSONIC JETS IN THE UPPER-ATMOSPHERE OF JUPITER

A new model to explain both the Ly-alpha bulge of Jupiter and the heat ing excess of the jovian upper atmosphere is presented. Based on an id ealized representation of the auroral activity, we precisely describe how thermospheric winds, which may form near the northern and southern oval maximum activity regions in the jovian aurora, could propagate a long the planet surface and collide at the jovian equator near 100 deg rees longitudinal system III. In this collision, part of the energy is converted to random wave motion and heat, and the remaining energy is transferred to two lateral outgoing jets. The random motion and heat enhance the atomic Ii cross section, explaining the excess observed fo r both the brightness and the width of the Ly-alpha line. The kinetic energy carried by the northern and southern jets spreads over the whol e planet surface as thermal energy, explaining the heating excess obse rved for the jovian upper atmosphere. The resulting dynamics and energ y budget of the jovian upper atmosphere are carefully described. (C) 1 995 Academic Press, Inc.