Cover Page/Proposal Summary

ROSS-99    NRA 99-OSS-01

Date Due: 5/3/99

In this proposal we request support to enable us to continue our studies of the interaction of the solar wind with Venus and Mars and other ionospheric processes at these planets. A significant fraction of our recent activities has centered on the development, in a systematic fashion, of the "best possible" MHD model to describe these interaction and ionospheric phenomena at Venus and Mars. Under our present grant we have reached the point that we have a two-fluid 3D MHD model on adaptively refined unstructured grids, in which the solar wind interacts with an ionosphere. While this model is a significant advance for studies of the solar wind interaction processes with non-magnetic planetary bodies, it requires a great deal of computer resources and thus the spatial resolution and the number of cases that we can run are limited. As the next step in our systematic evolutionary approach we plan, with the partial support of the new grant, to modify the numerical code to operate with a spherical grid structure. We also plan to move from a two to a three fluid formulation. These two changes, permit the use of a much better vertical resolution in the ionospheric region and the introduction of a more realistic ionosphere, both of which will lead to a better overall model. After a careful checkout of this modified code we will apply it to Mars and Venus. We will compare the model results with available and relevant data to establish the validity/limitations of these models and obtain new insights into the physical processes controlling the behavior of these regions. As opportunity arises, we will also undertake other related "studies of opportunities", as we have done successfully in the past (e. g. hot atom calculations, studies of ionospheric energetics).