Mars and Venus are our immediate neighbors and therefore they have an outstanding relevance. The European Space Agency ESA dedicated Mars and Venus the scientific space missions Mars-Express and Venus-Express, respectively. The TU of Braunschweig is involved in both of them with outstanding scientific contributions. In the NPS group models of the plasma environment are developed which combine simulation and observation results. Mars and Venus have a quite different size (Mars-radius=3397 km, Venus-radius=6052 km) but for the interaction with the solar wind other criteria are important. Both planets are surrounded by an ionosphere and they do not possess a noteworthy intrinsic magnetic field. These properties cause typical scales of the plasma interaction regions which are in the same order as the gyroradii of the ionospheric ions. Therefore the hybrid code is a very good choice for the simulation of the interaction processes.
The figure shows three-dimensional simulated plasma structures in the environment of Mars. The solar wind density is color coded and the streamlines of the velocity field are drawn black. The bow shock, the magnetosheath and a strong decrease of the solar wind density close to the planetary surface (dark blue) are clearly visible. This decrease is connected with a strong increase of the ionospheric density. It is important to note that the two plasma components do not merge but form a boundary layer, the so-called Ion Composition Boundary [Figure: Alexander Boesswetter, Dissertation TU Braunschweig, 2008].
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