Earth Planets Space, Vol. 64 (No. 2), pp. 113-120, 2012
E. Dubinin1, M. Fraenz1, J. Woch1, R. Modolo2, G. Chanteur3, F. Duru4, D. A. Gurnett4, S. Barabash5, and R. Lundin5
1MPI für Sonnensystemforschung, 37191 Katlenburg-Lindau, Germany
2LATMOS, UVSQ-CNRS-IPSL, Guyancourt, France
3Ecole Polytechnique-LPP, Palaiseau, France
4Department of Physics and Astronomy, Iowa University, Iowa, USA
5Swedish Institute of Space Physics, Kiruna, Sweden
(Received February 4, 2011; Revised May 6, 2011; Accepted May 18, 2011; Online published March 8, 2012)
The measurements carried out by the ASPERA-3 and MARSIS experiments on board the Mars Express (MEX) spacecraft show that the upper Martian ionosphere (h ≥ 400 km) is strongly azimuthally asymmetrical. There are several factors, e.g., the crustal magnetization on Mars and the orientation of the interplanetary magnetic field (IMF) which can give rise to formation of ionospheric swells and valleys. It is shown that expansion of the ionospheric plasma along the magnetic field lines of crustal origin can produce bulges in the plasma density. The absense of a magnetometer on MEX makes the retrieval of an asymmetry caused by the IMF more difficult. However hybrid simulations give a hint that the ionosphere in the hemisphere (E-) to which the motional electric field is pointed occurs more inflated than the ionosphere in the opposite (E+) hemisphere.
Key words: Mars, ionosphere, crustal magnetization, solar wind.