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M.G. Kivelson (UCLA/IGPP)
>From several close passes by Io, Galileo has provided a wealth of data on the magnetic and plasma environment of this remarkable body. Pickup ions load the flux tubes, their presence manifested by field depressions as well as by the production of ion cyclotron waves. These waves establish that molecular sources of ions not registered by spectroscopic means are present in Ioís surroundings out to many Io radii. Acceleration processes that produce field aligned electron distributions over a range of energy up to ~100 keV may relate to the signature of Io in the Jovian ionosphere. Because of the strong currents driven through the surrounding plasma by the interaction with Io and its exosphere, it has not been possible to establish whether Io has an internal magnetic field and therefore the nature (permanent or induced) of a possible field is still uncertain. Several opportunities to return to Io may occur in the final years of Galileoís exploration of Jupiterís magnetosphere. Possible trajectories would provide data from polar regions which should give clear indication of the presence or absence of a significant internal magnetic moment.
This work was partially supported by the Jet Propulsion Laboratory under contract JPL 958694 and by NASA under grant NAG5-7959.