GALILEO EVIDENCE FOR RAPID INTERCHANGE TRANSPORT IN THE IO TORUS

Anomalous plasma signatures were detected by the Galileo particles and fields instruments during the initial transit through the Io torus. T hese unusual events are characterized by abrupt changes in the magneti c field, enhanced levels of broadband low frequency electromagnetic wa ves and a pronounced change in both the flux and pitch angle anisotrop y of energetic particles. Here we present a coordinated study of one o f the events which occurred near 6.03R(J) just after 17:34 UT on Decem ber 7, 1995. The available data are consistent with the concept of rap id inward transport, and this is interpreted as the first evidence for the predicted interchange motions in the region exterior to the orbit of Io. Theoretical arguments indicate that the interchanging flux tub e is characterized by substantially reduced plasma density, a spatial scale comparable to 10(3) km, and an inward radial velocity comparable to 10(2) km/s.