Three-dimensional multispecies MHD studies of the solar wind interaction with Mars in the presence of crustal fields

We present the results of model calculations using a multispecies MHD model of the interaction of the solar wind with Mars. The three ions considered are H⁺, O₂⁺, and O⁺, representing the solar wind and the two major ionospheric ion species, respectively. The calculations indicate that the presence of a hot oxygen corona does not, within the resolution and accuracy of the model, lead to any significant effect on the dayside bow shock and ionopause positions. Next the trans-terminator fluxes and escape fluxes down the tail were calculated neglecting the effects of the crustal magnetic field. The calculated flux values are consistent with the measured escape fluxes and the calculated limiting fluxes from the dayside ionosphere. Finally, a 60-order harmonic expansion model of the measured magnetic field was incorporated into the model. The crustal magnetic field did not cause major distortions in the bow shock but certainly had an important effect within the magnetosheath and on the apparent altitude of the ionopause. The model results also indicated the presence of "minimagnetocylinders," consistent with the MGS observations. We also recalculated the trans-terminator and escape fluxes, for the nominal solar wind case, in the presence of the crustal magnetic field and found, as expected, that there is a decrease in the calculated escape flux; however, it is still reasonably close to the value estimated from the Phobos-2 observations.