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Science 20 September 1991:
Vol. 253. no. 5026, pp. 1394 - 1397
DOI: 10.1126/science.253.5026.1394
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Articles

Molecular Origin of Io's Fast Sodium

NICHOLAS M. SCHNEIDER 1, JOHN T. TRAUGER 2, JODY K. WILSON 1, DAVID I. BROWN 2, ROBIN W. EVANS 2, and DONALD E. SHEMANSKY 3

1 Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder, CO 80309-0392
2 Jet Propulsion Laboratory, Pasadena, CA 91109
3 Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ 85721

Neutral sodium emissions encircling Jupiter exhibit an intricate and variable structure that is well matched by a simple loss process from Io's atmosphere. These observations imply that fast neutral sodium is created locally in the Io plasma torus, both near Io and as much as 8 hours downstream. Sodium-bearing molecules may be present in Io's upper atmosphere, where they are ionized by the plasma torus and swept downstream. The molecular ions dissociate and dissociatively recombine on a short time scale, releasing neutral fragments into escape trajectories from Jupiter. This theory explains a diverse set of sodium observations, and it implies that molecular reactions (particularly electron impact ionization and dissociation) are important at the top of Io's atmosphere.

Submitted on June 27, 1991
Accepted on August 7, 1991


THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES:
Response of the Io plasma torus to comet Shoemaker-Levy 9.
M. McGrath, D. Hall, P. Matheson, H. Weaver, J. Trauger, T. Smith, N Thomas, R Gladstone, N. Schneider, W. Harris, et al. (1995)
Science 267, 1313-1317
   Abstract »    PDF »
Imaging Obsearvations of Jupiter's Sodium Magneto-Nebula During the Ulysses Encounter.
M. Mendillo, B. Flynn, and J. Baumgardner (1992)
Science 257, 1510-1512
   Abstract »    PDF »


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