Mars Back Positive Surface Electron Precipitation On The Ionosphere

Based on full investigation and study on Mars space simulation as well as its space environment exploration, using the result from the single-fluid ideal MHD model about the Mars space simulation, this paper has studied Mars space magnetic field structure and the influence of Marian surface crustal magnetic field on the magnetic field structure; determined the possible precipitation area of the solar wind electron in the nightside martian atmosphere according to the single particle trajectory theory; And analyzed the electron impact ionization to estimate the height of the nightside Martian ionosphere peak and the electron density distribution using the energy flux analysis method.In the interaction process of solar wind and Mars, the interplanetary magnetic field lines are curved and'draping'around the planet, The majority of magnetic field lines bypass over two poles, leaving'V shaped'structure in the wake behind Mars. Near the surface of Mars, the local crustal magnetic fields also have noticeable influence on the magnetic field structure. The crustal magnetic fields at different positions, with different intensities form the dissimilar magnetic filed structure and mini-magnetospheres when interacting with the solar wind. The local crustal magnetic fields change the morphology of the magnetic field, and accordingly may play important role in determining the plasma distribution.The solar wind electron moves along the magnetic line of solar wind plasma,'V shaped'structure of the magnetic field line, to precipitate to the Martian atmosphere and then impact ionization happens. The precipitation regions lie at the nightside of the Mars, near the dusk. Two precipitation regions are quite narrow and small. This possibly causes Mars nightside ionosphere unstable, and the scope is not big.The solar wind electron precipitates along the magnetic line to the Martian nightside atmosphere, impacts and ionizes the neutrals at the altitude of 130~500km. Under the case which obtained from Phobos-2, The height of ionization peak is around 170km, and the ionospheric electron density at the peak is 3.4×103cm-3. At the same time this paper exam the influence of the electron energy and electron energy density to the height of ionization peak and electron density. The simulation result is consistent with the result from Mas 4/5 and Viking occultaion measurement.