Galileo-measured depletion of near-Io hot ring current plasmas since the Voyager epoch

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Read Full Article Cited by JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 103, NO. A3, PAGES 4715–4722, 1998 Galileo-measured depletion of near-Io hot ring current plasmas since the Voyager epoch B. H. Mauk Applied Physics Laboratory, Johns Hopkins University, Laurel, Maryland R. W. McEntire Applied Physics Laboratory, Johns Hopkins University, Laurel, Maryland D. J. Williams Applied Physics Laboratory, Johns Hopkins University, Laurel, Maryland A. Lagg Max Planck Institute for Aeronomy, Katlenburg-Lindau, Germany E. C. Roelof Applied Physics Laboratory, Johns Hopkins University, Laurel, Maryland S. M. Krimigis Applied Physics Laboratory, Johns Hopkins University, Laurel, Maryland T. P. Armstrong Department of Physics and Astronomy, University of Kansas, Lawrence, Kansas T. A. Fritz Center for Space Physics, Boston University, Boston, Massachusetts L. J. Lanzerotti Bell Laboratories, Lucent Technologies, Murray Hill, New Jersey J. G. Roederer Geophysical Institute, University of Alaska, Fairbanks, Alaska B. Wilken Max Planck Institute for Aeronomy, Katlenburg-Lindau, Germany Abstract The first mass-discriminated, hot ion distribution moments (pressure, energy intensity) are determined for hot >50-keV ions in Jupiter's inner magnetosphere at the outer edge of Io's plasma torus by using the Galileo energetic particle detector (EPD) data. These hot plasmas were significantly depleted during the Galileo encounter in 1995 as compared with the Voyager epoch of 1979. The depletion of the hot ions is apparently caused by enhanced charge exchange losses of hot ions, perhaps associated with enhanced emissions of neutral gases from the volcanoes of Io. Such neutral gas enhancements could simultaneously explain increases, reported elsewhere, in the densities of the cooler Io torus plasmas. The hot plasma changes may explain why radial transport interchange turbulence has been observed by Galileo in the Io torus regions, whereas such turbulence was not apparent during the Voyager encounters in 1979. The hot ion depletion could also play a role in explaining the apparent differences between the Jovian auroral configuration observed in recent years by the Hubble space telescope and ground observers and the configuration observed by Voyager. This possibility is much less certain, however. Received 24 April 1997; accepted 14 August 1997. Read Full Article Cited by Citation: Mauk, B. H., et al. (1998), Galileo-measured depletion of near-Io hot ring current plasmas since the Voyager epoch, J. Geophys. Res., 103(A3), 4715–4722. Copyright 1998 by the American Geophysical Union.

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