Mesospheric Hydrogen Related to Exospheric Escape Mechanisms

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Abstract
The thermal escape rate of hydrogen inferred from exospheric density measurements is too low by a factor of at least 2 to accord with the mixing ratio of H2O, H2 and CH4 observed in the stratosphere and mesosphere. The effect on the mixing ratio of adding hydrogen fluxes to support the polar wind by lateral flow and to supply a loss to charge transfer with fast protons is investigated. It is shown that these additional mechanisms can make up the deficit. The exobase hydrogen density must adjust locally to supply hydrogen to the three separate escape mechanisms at the rate demanded by the mixing ratio in the lower atmosphere and the exospheric temperature. Abstract The thermal escape rate of hydrogen inferred from exospheric density measurements is too low by a factor of at least 2 to accord with the mixing ratio of H2O, H2 and CH4 observed in the stratosphere and mesosphere. The effect on the mixing ratio of adding hydrogen fluxes to support the polar wind by lateral flow and to supply a loss to charge transfer with fast protons is investigated. It is shown that these additional mechanisms can make up the deficit. The exobase hydrogen density must adjust locally to supply hydrogen to the three separate escape mechanisms at the rate demanded by the mixing ratio in the lower atmosphere and the exospheric temperature.

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