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GEOPHYSICAL RESEARCH LETTERS, VOL. 24, NO. 17, PAGES 2131–2134, 1997

Galileo Evidence for Rapid Interchange Transport in the Io Torus

R. M. Thorne

Dept. of Atmospheric Sciences, University of California, Los Angeles


T. P. Armstrong

Dept. of Physics and Astronomy, University of Kansas, Lawrence


S. Stone

Dept. of Physics and Astronomy, University of Kansas, Lawrence


D. J. Williams

The Johns Hopkins University, Applied Physics Laboratory, Laurel, Maryland


R. W. McEntire

The Johns Hopkins University, Applied Physics Laboratory, Laurel, Maryland


S. J. Bolton

Jet Propulsion Laboratory, Pasadena, California


D. A. Gurnett

Dept. of Physics and Astronomy, The University of Iowa, Iowa City


M. G. Kivelson

Institute of Geophysics and Planetary Physics, University of California, Los Angeles


Abstract

Anomalous plasma signatures were detected by the Galileo particles and fields instruments during the initial transit through the Io torus. These unusual events are characterized by abrupt changes in the magnetic field, enhanced levels of broadband low frequency electromagnetic waves and a pronounced change in both the flux and pitch angle anisotropy of energetic particles. Here we present a coordinated study of one of the events which occurred near 6.03RJ just after 17:34 UT on December 7, 1995. The available data are consistent with the concept of rapid 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 tube is characterized by substantially reduced plasma density, a spatial scale comparable to 10³ km, and an inward radial velocity comparable to 10² km/s.

Received 20 March 1997; accepted 7 May 1997.

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Citation: Thorne, R. M., T. P. Armstrong, S. Stone, D. J. Williams, R. W. McEntire, S. J. Bolton, D. A. Gurnett, and M. G. Kivelson (1997), Galileo Evidence for Rapid Interchange Transport in the Io Torus, Geophys. Res. Lett., 24(17), 2131–2134.