Evidence for a magnetosphere at Ganymede from plasma-wave observations by the Galileo spacecraft (original) (raw)

Nature volume 384, pages 535–537 (1996)Cite this article

Abstract

ON 27 June 1996 the Galileo spacecraft1,2 made the first of four planned close fly-bys of Ganymede, Jupiter's largest moon. Here we report measurements of plasma waves and radio emissions, over the frequency range 5 Hz to 5.6 MHz during the first encounter. Intense plasma waves were detected over a region of space nearly four times Ganymede's diameter, which is much larger than would be expected for a simple wake arising from Ganymede's passage through Jupiter's rapidly rotating magneto-sphere. The types of waves detected (whistler-mode emissions, upper hybrid waves, electrostatic electron cyclotron waves and escaping radio emission) strongly suggest that Ganymede has a large, extended magnetosphere of its own. The data indicate the presence of a strong (B > 400 nT) magnetic field, and show that Ganymede is surrounded by an ionosphere-like plasma with a maximum electron density of about 100 particles cm−3 and a scale height of about 1,000km.

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Authors and Affiliations

  1. Department of Physics and Astronomy, University of Iowa, Iowa City, Iowa, 52242, USA
    D. A. Gurnett & W. S. Kurth
  2. Centre d'Etudes des Environnements Terrestre et Planetaires, Universite Versailles Saint Quentin, 10/12 Avenue de I'Europe, 78140, Velizy, France
    A. Roux
  3. Jet Propulsion Laboratory, 4800 Oak Grove Drive, Pasadena, California, 91109, USA
    S. J. Bolton
  4. Office of the Chancellor, UCLA, Los Angeles, California, 90095, USA
    C. F. Kennel

Authors

  1. D. A. Gurnett
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  2. W. S. Kurth
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  3. A. Roux
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  4. S. J. Bolton
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  5. C. F. Kennel
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Gurnett, D., Kurth, W., Roux, A. et al. Evidence for a magnetosphere at Ganymede from plasma-wave observations by the Galileo spacecraft.Nature 384, 535–537 (1996). https://doi.org/10.1038/384535a0

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