The role of the superthermal ions in the dayside postshock ionospheric flow field at Venus is investigated in a 2-D model by integrating the equation of motion of a superthermal population of O$\sp+$ test particles and statistically examining their contribution to the altitude variation of number density and horizontal current distribution. The model reveals superthermal ions $\vec {\rm E} \times \vec {\rm B}$ drifting downward and gradient drifting horizontally with attendant currents. Regions of "wrapped up" plasma known as fluxropes and identified previously as resulting from Kelvin-Helmholtz instability in the ionosphere are found to significantly scatter ions and limit the horizontal currents. Monte-Carlo simulation of charge exchange and subsequent neutral-on-neutral collision processes produce a substantial vertical flux of ballistic neutrals with hyperbolic trajectories possibly representing a heretofore unrecognized atmospheric loss mechanism at Venus. Modeled altitude profiles of superthermal density superficially agree with empirical analysis by Stewart (1991) for a "missing" pressure term in the momentum balance requirements. (Abstract shortened with permission of author.)
| Identifer | oai:union.ndltd.org:RICE/oai:scholarship.rice.edu:1911/13676 |
| Date | January 1992 |
| Creators | Kramer, Leonard |
| Contributors | Cloutier, Paul A. |
| Source Sets | Rice University |
| Language | English |
| Detected Language | English |
| Type | Thesis, Text |
| Format | 73 p., application/pdf |
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