An explanation of the east–west asymmetry of Io's sodium cloud (original) (raw)

Nature volume 322, pages 343–345 (1986)Cite this article

Abstract

Since the discovery of a cloud of neutral sodium atoms accompanying the jovian satellite, Io, in its orbit1, asymmetries of part of the cloud (region B)2 have often been noted3–6. Brightness variations with orbital longitude3,4 and asymmetries found by comparing images taken at orbital longitudes differing by 180° (ref. 5) have been explained as effects of solar radiation pressure7. Given that the vast majority of neutrals precede Io in its orbit, and that sputtering of Io is the principal source mechanism, Matson _et al._8 postulated a hemispherical source centred 60° towards the sub-Jupiter point from the centre of the leading hemisphere to explain the general cloud shape. However, soft collisions with plasma ions may be important and call for a reassessment9. I show here that, given reasonable assumptions, the east–west brightness asymmetry can be explained by temporal changes in the number of emitting atoms in the cloud caused by atmospheric shielding of the surface.

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References

  1. Brown, R. A. in Exploration of the Planetary System (eds Woszczyk, A. & Iwaniszewska, C.) 527–531 (Reidel, Hingham, 1974).
    Book Google Scholar
  2. Brown, R. A., Goody, R. M., Murcray, F. J. & Chaffee, F. H. Astrophys. J. 200, L49–L53 (1975).
    Article ADS CAS Google Scholar
  3. Bergstralh, J. T., Matson, D. L. & Johnson, T. V. Astrophys. J. 195, L131–L135 (1975).
    Article ADS CAS Google Scholar
  4. Bergstralh, J. T., Young, J. W., Matson, D. L. & Johnson, T. V. Astrophys. J. 211, L51–L55 (1977).
    Article ADS CAS Google Scholar
  5. Goldberg, B. A., Garneau, G. W. & LaVoie, S. K. Science 226, 512–516 (1984).
    Article ADS CAS Google Scholar
  6. Murcray, F. J. & Goody, R. M. Astrophys. J. 226, 327–335 (1978).
    Article ADS CAS Google Scholar
  7. Smyth, W. H. Astrophys. J. 234, 1148–1153 (1979).
    Article ADS CAS Google Scholar
  8. Matson, D. L., Goldberg, G. A., Johnson, T. V. & Carlson, R. W. Science 199, 531–533 (1978).
    Article ADS CAS Google Scholar
  9. Brown, R. A., Pilcher, C. B. & Strobel, D. F. in Physics of the Jovian Magnetosphere (ed. Dessler, A. J.) 197–225 (Cambridge University Press, 1983).
    Book Google Scholar
  10. Matson, D. L. & Nash, D. B. J. geophys. Res. 88, 4771–4783 (1983).
    Article ADS CAS Google Scholar
  11. Johnson, R. E., Garret, J. W., Boring, J. W., Barton, L. A. & Brown, W. L. J. geophys. Res. 89, B711–B715 (1984).
    Article Google Scholar
  12. Kumar, S. J. geophys. Res. 89, 7399–7406 (1984).
    Article ADS Google Scholar
  13. Cheng, A. F. J. geophys. Res. 89, 3939–3944 (1984).
    Article ADS CAS Google Scholar
  14. Kumar, S. Icarus 61, 101–123 (1985).
    Article ADS CAS Google Scholar
  15. Kliore, A. J. et al. Icarus 24, 407–410 (1975).
    Article ADS Google Scholar
  16. Kliore, A. J. IAU Colloq. 57 (1980).
  17. Minton, R. B. Commun. lunar planet. Lab. 10, 35–39 (1973).
    ADS Google Scholar
  18. Pearl, J. et al. Nature 280, 755–758 (1979).
    Article ADS CAS Google Scholar
  19. Fanale, F. P., Banerdt, W. B., Elson, L. S., Johnson, T. V. & Zurek, R. W. in The Satellites of Jupiter (ed. Morrison, D.) 756–781 (University of Arizona Press, Tucson, 1982).
    Google Scholar
  20. Honig, R. E. & Hook, H. O. RCA Rev. 21, 360–368 (1960).
    CAS Google Scholar
  21. Kumar, S. & Hunten, D. in The Satellites of Jupiter (ed. Morrison, D.) 782–806 (University of Arizona Press, Tucson, 1982).
    Google Scholar
  22. Cummings, W. D., Dessler, A. J. & Hill, T. W. J. geophys. Res. 85, 2108–2114 (1980).
    Article ADS Google Scholar
  23. Nash, D. B. & Johnson, T. V. Icarus 38, 69–74 (1979).
    Article ADS Google Scholar
  24. Moore, M. H. Icarus 59, 114–128 (1984).
    Article ADS CAS Google Scholar
  25. Radford, H. E. & Rice, F. O. J. chem. Phys. 33, 774–776 (1960).
    Article ADS CAS Google Scholar
  26. Young, A. T. Icarus 58, 197–226 (1984).
    Article ADS CAS Google Scholar
  27. Soderblom, L. A. et al. Geophys. Res. Lett. 7, 963–966 (1980).
    Article ADS CAS Google Scholar
  28. Howell, R. R., Cruikshank, D. P. & Fanale, F. P. Icarus 57, 83–92 (1984).
    Article ADS CAS Google Scholar
  29. Nelson, R. M. et al. Science 210, 784–786 (1980).
    Article ADS CAS Google Scholar
  30. Shemansky, D. E. Astrophys. J. 236, 1043–1054 (1980).
    Article ADS CAS Google Scholar
  31. Trafton, L. & Macy, W. Astrophys. J. 215, 971–976 (1977).
    Article ADS CAS Google Scholar
  32. Bagenal, F. & Sullivan, J. D. J. geophys. Res. 86, 8447–8466 (1981).
    Article ADS CAS Google Scholar

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Authors and Affiliations

  1. Rock Cottage, Kinnerley, Oswestry, SY10 8DF, UK
    Nicolas Thomas

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Thomas, N. An explanation of the east–west asymmetry of Io's sodium cloud.Nature 322, 343–345 (1986). https://doi.org/10.1038/322343a0

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