Solar Wind Interaction with Planetospheres and Cometary Exospheres

Monio Kartalev

Geospace Hydrodynamics Laboratory, Institute of Mechanics, Bulgarian Academy of Sciences, Bulgaria

Some advantages of the 'modular' approach in modeling of the solar wind interaction with planetospheres (magnetospheres or ionospheres) and cometary exospheres are discussed. This method provides the possibility to describe, if necessary, different regions of the interaction in different model approaches.

In the presented example of the solar wind interaction with the Earth's magnetosphere, the magnetosheath is modeled in 3D gasdynamic approach, while a modification Tsyganenko model is utilized for the magnetosphere. The shock wave and magnetopause geometries are obtained self-consistently as a part of the solution. Many comparisons with CLUSTER and Interball measurements confirm the coincidence with predicted (under certain solar wind conditions) geometries of the magnetosheath boundaries even in such details as magnetopause cusp indentations. Besides the realistic 3D magnetosheath, the approach provides a modified Tsyganenko model with realistic magnetopause and numerically obtained shielding magnetic field.

The gasdynamic module of the models in the case of the SW interaction with nonmagnetic planets and comets, where the mass-loading process becomes very essential, requires inclusion the terms, describing source and sink photo-chemical processes in the equations. The contribution of these processes could be different in separated region of interaction. It is demonstrated on the example of the SW-Venus interaction that the creation of the planetosphere (ionosphere) ionized gas is only due to the ionization in the planetary neutral exosphere. A self-consistent numerical modeling of the planetosphere and planetosheath (ionosheath) with mass-loading process included in both regions provides the parameters' distribution (dynamics) there along with the self-consistent boundary (planetopause).

The utilized 'grid-characteristic' explicit first-order non-conservative finite difference scheme ensures in the simulation of the SW-comet Halley interaction better than in other approaches coincidence with the Giotto measurements in the inner comet coma. A new interpretation of the so called diamagnetic cavity boundary is proposed, proving that this is rather the inner shock wave. The latter statement is based on the introduction (discovering) of a new kind of magnetic field diffusion caused by the specifics of the mass-loading process and directed against the neutral particles flow.