On the origin of Jovian decameter radio bursts

Jovian "millisecond" or "S" bursts are intense impulsive decameter radio spikes, drifting in frequency in tens of milliseconds over several MHz, which generation scenario has been much debated for 30 years. The result of automated recognition and analysis applied to an extensive set of ground-based digital high-resolution observations of these bursts strongly favours an emission mechanism and scenario: Cyclotron-Maser emission of electron populations accelerated near Io, and then in quasi-adiabatic motion along magnetic field lines connecting Io's magnetospheric wake to Jupiter's amoral regions. In this frame, the energy and pitch angle of radiating electrons, the location of the field lines along which they emit radio waves with respect to Io's flux tube, and the radiosources extent are deduced from radio measurements. However, when compared to the results of Voyager in-situ exploration of Io's vicinity, and to recent InfraRed and Far-UltraViolet observations of the Io flux: tube footprint, the Cyclotron-Maser mechanism meets an "energy crisis". On another hand, the very fine frequency-time structure of S-bursts displays complex patterns, here interpreted as the signature of small-scale and short-lived density and/or acceleration structures, while their average properties are attributed to the magnetic field topology near the IFT and the sharp emission beaming.