Skip to main content

Thank you for visiting You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

Evidence for a magnetosphere at Ganymede from plasma-wave observations by the Galileo spacecraft


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.

Access options

Rent or Buy article

Get time limited or full article access on ReadCube.


All prices are NET prices.


  1. 1

    Johnson, T. V., Yeates, C. M. & Young, R. Space Sci. Rev. 60, 3–21 (1992).

    ADS  Article  Google Scholar 

  2. 2

    Gurnett, D. A. et al. Space Sci. Rev. 60, 341–355 (1992).

    ADS  Article  Google Scholar 

  3. 3

    Stix, T. H. The Theory of Plasma Waves 12 (McGraw-Hill, New York, 1962).

    MATH  Google Scholar 

  4. 4

    Kennel, C. F. & Petschek, H. E. J. Geophys. Res. 71, 1–28 (1966).

    ADS  Article  Google Scholar 

  5. 5

    Helliwell, R. A. Whistlers and Related Ionospheric Phenomena 207 (Stanford Univ. Press, Stanford, 1965).

    Google Scholar 

  6. 6

    Kurth, W. S. & Gurnett, D. A. J. Geophys. Res. 96, 18977–18991 (1991).

    ADS  Article  Google Scholar 

  7. 7

    Burtis, W. J. & Helliwell, R. A. J. Geophys. Res. 74, 3002–3010 (1969).

    ADS  Article  Google Scholar 

  8. 8

    Kivelson, M. G. et al. Nature 384, 537–541 (1996).

    ADS  CAS  Article  Google Scholar 

  9. 9

    Scarf, F. L., Gurnett, D. A. & Kurth, W. S. Nature 292, 747–750 (1981).

    ADS  Article  Google Scholar 

  10. 10

    Gurnett, D. A. et al. J. Geophys. Res. 84, 7043–7058 (1979).

    ADS  Article  Google Scholar 

  11. 11

    Walsh, D., Haddock, T. F. & Schulte, H. F. Space Res. 4, 935–959 (1964).

    Google Scholar 

  12. 12

    Mosier, S. R., Kaiser, M. L. & Brown, L. W. J. Geophys. Res. 78, 1673–1677 (1973).

    ADS  Article  Google Scholar 

  13. 13

    Warwick, J. W. et al. Science 204, 995–998 (1979).

    ADS  CAS  Article  Google Scholar 

  14. 14

    Gurnett, D. A. J. Geophys. Res. 86, 8199–8212 (1981).

    ADS  Article  Google Scholar 

  15. 15

    Noll, K. S., Johnson, R. E., Lane, A. L., Domingua, D. L. & Weaver, H. A. Science 273, 341–343 (1996).

    ADS  CAS  Article  Google Scholar 

  16. 16

    Kennel, C. F., Scarf, F. L., Fredericks, R. W., McGehee, J. H. & Coroniti, F. V. J. Geophys. Res. 75, 6136–6152 (1970).

    ADS  Article  Google Scholar 

  17. 17

    Ashour-Abdalla, M., Chanteur, G. & Pellat, R. J. Geophys. Res. 80, 2775–2782 (1975).

    ADS  Article  Google Scholar 

  18. 18

    Rönnmark, K., Borg, H., Christiansen, P. J., Gough, M. P. & Jones, D. Space Sci. Rev. 22, 401–417 (1978).

    ADS  Article  Google Scholar 

  19. 19

    Gurnett, D. A. J. Geophys. Res. 80, 2751–2763 (1975).

    ADS  Article  Google Scholar 

  20. 20

    Gurnett, D. A. & Frank, L. A. J. Geophys. Res. 81, 3875–3885 (1976).

    ADS  Article  Google Scholar 

  21. 21

    Kaiser, M. L. & Desch, M. D. J. Geophys. Res. 87, 389–392 (1980).

    Google Scholar 

  22. 22

    Melrose, D. B. J. Geophys. Res. 86, 30–36 (1981).

    ADS  Article  Google Scholar 

  23. 23

    Van Allen, J. A. et al. Science 183, 309–311 (1974).

    ADS  CAS  Article  Google Scholar 

  24. 24

    Krimigis, S. M. et al. Science 204, 998–1003 (1979).

    ADS  CAS  Article  Google Scholar 

  25. 25

    Lanzerotti, L. J. et al. Science 257, 1518–1524 (1992).

    ADS  CAS  Article  Google Scholar 

  26. 26

    Cowen, R. Science News 150, 181 (1996).

    Article  Google Scholar 

Download references

Author information



Rights and permissions

Reprints and Permissions

About this article

Cite this article

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).

Download citation

Further reading


By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.


Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing