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J. E. P. Connerney (NASA GSFC), T. Satoh (Science University of Tokyo), J. T. Clarke (University of Michigan)
Observations of Jovian aurora reveal a wealth of information about Jupiter's magnetic field, magnetosphere, and magnetospheric dynamics. The interaction between Jupiter's magnetic field and the satellite Io drives million-Ampere currents along magnetic field lines into the Jovian ionosphere. These currents excite localized emissions in the IR and UV at the foot of the Io Flux Tube (IFT), the observation of which provides clues to the nature of the interaction. At some system 3 longitudes (of Io), the foot leads an undisturbed field line by some 10 to 15 degrees, as predicted by Goldreich and Lynden-Bell (1969) and at odds with the Alfven propagation models (e.g., Neubauer, 1981). However, at other longitudes small leads and multiple footprints are evident, as predicted by the Alfven propagation models. It appears that the Io interaction can take both forms, not simply related to Io's position relative to the centrifugal equator as anticipated. Other emissions, at times greatly exceeding those associated with the instantaneous IFT foot, can be found along it's path (but not where you'd expect them).