THE GLOBAL PLASMA ENVIRONMENT OF IO AS INFERRED FROM THE GALILEO PLASMA-WAVE OBSERVATIONS

We take advantage of a partial and a total occultation of the jovian r adio sources observed during the flyby of Io to characterize the plasm a environment of this moon. We show that it presents a strong upstream / downstream asymmetry. A dense plasma structure (n > 5x10(4) cm(-3)) extends far from Io (at least 1000 km) in the wake direction whereas no extended dense region is found upstream. The dense region in the wa ke could correspond to a the stagnation region of the flow of the coro tating plasma.