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Science 18 October 1996:
Vol. 274. no. 5286, pp. 401 - 403
DOI: 10.1126/science.274.5286.401
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Reports

Electron Beams and Ion Composition Measured at Io and in Its Torus

D. J. Williams, * B. H. Mauk, R. E. McEntire, E. C. Roelof, T. P. Armstrong, B. Wilken, J. G. Roederer, S. M. Krimigis, T. A. Fritz, L. J. Lanzerotti

Intense, magnetic field-aligned, bidirectional, energetic (>15 kiloelectron volts) electron beams were discovered by the Galileo energetic particles detector during the flyby of Io. These beams can carry sufficient energy flux into Jupiter's atmosphere to produce a visible aurora at the footprint of the magnetic flux tube connecting Io to Jupiter. Composition measurements through the torus showed that the spatial distributions of protons, oxygen, and sulfur are different, with sulfur being the dominant energetic (>sim 10 kiloelectron volts per nucleon) ion at closest approach.

D. J. Williams, B. H. Mauk, R. E. McEntire, E. C. Roelof, S. M. Krimigis, Johns Hopkins Applied Physics Laboratory, Johns Hopkins Road, Laurel, MD 20723, USA.
T. P. Armstrong, Department of Physics and Astronomy, University of Kansas, Lawrence, KA 66045, USA.
B. Wilken, Max Planck Institute for Aeronomy, 37189 Katlenburg-Lindau, Germany.
J. G. Roederer, Geophysical Institute, University of Alaska, Fairbanks, AK 99775, USA.
T. A. Fritz, Boston University, Center for Space Physics, Boston, MA 02215, USA.
L. J. Lanzerotti, Lucent Technologies, 600 Mountain Avenue, Murray Hill, NJ 07974, USA.
*   To whom correspondence should be addressed. E-mail: djw{at}aplcomm.jhuapl.edu

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THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES:
Detection of SO in Io's Exosphere.
C. T. Russell and M. G. Kivelson (2000)
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Far-Ultraviolet Imaging Spectroscopy of Io's Atmosphere with HST/STIS.
F. L. Roesler, H. W. Moos, R. J. Oliversen, R. C. Woodward Jr., K. D. Retherford, F. Scherb, M. A. McGrath, W. H. Smyth, P. D. Feldman, and D. F. Strobel (1999)
Science 283, 353-357
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Galileo Plasma Wave Observations in the Io Plasma Torus and Near Io.
D. A. Gurnett, W. S. Kurth, A. Roux, S. J. Bolton, and C. F. Kennel (1996)
Science 274, 391-392
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