MHD Models of Io's Interaction with the Plasma Torus: Comparison with the Polar Flybys

The original flyby of the Galileo spacecraft past Io in December, 1995 gave unprecedented observations, but in many ways these measurements raised more questions than they answered. In particular, the plasma-interaction signature in the magnetic field measurements was consistent with an intrinsic magnetic field at Io, but this was not the only possible explanation for the results. During the I27 flyby (February, 2000), Galileo probed a region on the flanks of Io that was sensitive to differences between the magnetized model of Io and the conducting model of Io. Based on the modeling of the Io interaction for this encounter, it seems unlikely that there is significant intrinsic magnetization at Io. The August, 2001 and October 2001 passes over the poles of Io should either confirm or refute these results. We will present comparisons of MHD model results with data from the new Galileo flybys and assess the likelihood of intrinsic magnetization at Io. Research Supported by NASA.