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Charge exchange in a planetary corona - Its effect on the distribution and escape of hydrogenThe theory for a spherical collisionless planetary corona is extended to include charge-exchange collisions between H(+) and H, which are assumed to constitute intermingled gases with different kinetic temperatures. The treatment is based on the conventional concept of a critical level (or exobase) above which the only collisions considered in the Boltzmann equation are those that resonantly exchange charge. Although the geometry treated is an oversimplification for a real planet, numerical examples are given for an idealized earth and Venus. For earth, an ion temperature of 4 times the neutral temperature, an ion density at the exobase of 14,000 per cu cm, and a plasmapause at 1.5 earth radii will raise the escape flux of H by a factor of 6. The total H above the exobase is changed by less than 1%. For Venus, conditions are examined that would account for the peculiar H distribution observed from Mariner 5. The plasma conditions required are not obviously outrageous by terrestrial standards, but the Mariner 5 ionosphere measurements did not show a high plasmapause at, say, 1.25 or 1.5 planetary radii, a fact that might argue against a charge-exchange model.
Document ID
19770038232
Document Type
Reprint (Version printed in journal)
Authors
Chamberlain, J. W. (Rice University Houston, Tex., United States)
Date Acquired
August 9, 2013
Publication Date
January 1, 1977
Publication Information
Publication: Journal of Geophysical Research
Volume: 82
Subject Category
LUNAR AND PLANETARY EXPLORATION
Distribution Limits
Public
Copyright
Other