A SCENARIO FOR JOVIAN S-BURSTS

Jovian S-bursts are intense impulsive decameter radio spikes drifting in frequency in tens of milliseconds over several hundreds of kHz up t o a few MHz. Their generation scenario has been much debated for 30 ye ars. The automated analysis of an extensive set of digital radio obser vations at very high temporal and spectral resolutions is presented he re. It strongly suggests that S-bursts are the cyclotron-maser emissio n of electron populations with similar to 5 keV energy, accelerated ne ar Io and then in quasi-adiabatic motion along magnetic field lines co nnecting the Io torus to Jupiter's auroral regions. This scenario is c onsistent with Voyager observations of Alfven waves near Io's wake and with recent infrared observations of the Io flux tube footprint. The total energy, velocity and pitch angle of the radiating electrons, and the extent of the bursts radiosources are deduced from the radio meas urements, which appear as a promising remote sensing tool for the Jovi an magnetosphere, and possibly that of other ''radio'' planets.