POSSIBLE ROLE OF ELECTROMAGNETIC LOW-FREQUENCY WAVES IN THE IO TORUS IN THE PRODUCTION OF JOVIAN AURORAE

The possible role of ULF waves observed in the Io torus in the generat ion of Jovian aurorae is investigated. Auroral emissions have been obs erved, not only at high latitude, but also at the footprint of magneti c field lines connected to the Io torus in a limited longitudinal rang e around 150 degrees. As Ulysses passed by Jupiter, it explored the Io torus in latitude and longitude, allowing to test a possible localiza tion of the waves on field lines mapping down into the aurora. A maxim um intensity of the waves is observed in the high latitude part of the torus around the longitude where the aurorae were observed. Another m aximum is also observed at the magnetic equator. The propagation mode of the waves is discussed and their amplitude is compared to the value s necessary for scattering ions, showing that the ULF waves could poss ibly be at the origin of the aurorae. (C) 1997 Elsevier Science Ltd.