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S.M. Krimigis, D.G. Mitchell (Applied Physics Laboratory, The Johns Hopkins University, Laurel, MD), D.C. Hamilton (Dept. of Physics, University of Maryland, College Park, MD), S. Livi (Applied Physics Laboratory, The Johns Hopkins University, Laurel, MD)
Observations are presented from the Magnetospheric Imaging Instrument (MIMI) onboard the Cassini spacecraft during its flyby of Jupiter (closest approach December 30, 2000). Two novel sensors have identified (a) a fast, hot magnetospheric neutral wind extending to large (>0.5 AU) distances from the planet, and (b) ions resulting from photoinization of neutrals, both hot and cold, that were picked up and accelerated by the solar wind electric field. Through imaging of the fast wind, a picture of the distribution of neutrals and their source, centered around Jupiter and enveloping the Io torus, has been discovered. The fast neutral wind results from charge exchange of energetic ions trapped in Jupiter's magnetosphere with resident slow neutrals and subsequent escape into cis-Jovian space. The pickup ions are found to be of a species and charge state (O+, S+, SO2+) characteristic of those identified with Io's plasma torus. Thus the space around Jupiter is permeated by Iogenic gas, resembling a large nebula that follows Jupiter as it orbits around the Sun.