On the Escape of Ions from the Venus Ionosphere
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Using high and low solar activity models of the Venus ionosphere, We compute the upper limits to the upward fluxes of ions. In a 1-D model, these fluxes probably represent the divergence of the horizontal ion fluxes, except near the subsolar point. The maximum transterminator fluxes are determined by the production rate of ions above the photochemical equilibrium boundary. The transterminator ion fluxes at low altitudes may converge on the nightside and flow downward, producing the nightside ionosphere. Some of the ionfluxes may escape from the gravitational field of the planet. We compare our upper limits to the transterminator ion fluxes measured by the RPA on Pioneer Venus, and estimates of the fluxes necessary to produce the observed nightside ionosphere. If data are available, we will compare our maximum fluxes to those measured by the Venus Express spacecraft. We also consider the effect of the upward fluxes on the measured and model ion density profiles. We find, that unlike Mars at low solar activity, fluxes close to the maxima are not necessary to reproduce the measured ion density profiles.
Fox, J. L.
(2007). On the Escape of Ions from the Venus Ionosphere. Eos, 88 (23 - Joint Assembly Supplement).