The nature of the martian ‘obstacle boundary’ Original Research Article

The measurements made by the Mars Global Surveyor have determined the Marsʹs magnetic moment M≤1011 Tm3. This value is, at least, one order of magnitude below the value originally estimated from the pressure balance under the assumption that the observed solar wind obstacle boundary is identical with the earth-like magnetopause. This obvious discrepancy offers the limits of classical MHD for description of the solar wind/Mars interaction and calls for new theoretical models. To describe the main physical processes during the ‘collision’ of the solar wind with the continuously produced cold heavy-ion plasmas of planetary origin, a bi-ion fluid model is used. It is shown that a sharp electrostatic barrier is formed between the two plasmas with following properties: stoppage of the proton flow and change of the ion composition, pile-up of the magnetic field, a decrease of the electron temperature. These characteristic features are seen in single-instrument analysis of the Phobos-2 and MGS data.