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

Abstract

[1] 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 + , O 2 + , 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.

Modeling of Venus, Mars, and Titan

“…Ma et al (2002) also described the general circulation of ionospheric plasma which, in agreement simulations of Venus' plasma interaction, was upward on the day side ionosphere, day to night at higher altitudes, downward on the night side below about 250 km altitude, and down Mars magnetotail at higher altitudes. Ma et al (2004) improved on the model published in Ma et al (2002) by including a new spherical grid structure, better resolution near the inner boundary, and an additional species (CO + 2 ). This model was used to quantify ion outflow from Mars for several orientations of crustal magnetic field and for different solar wind conditions.…”

“…The strongest of the magnetic fields (which occur mostly in the southern hemisphere) were placed in the sub-ram direction. Ma et al (2002) found that crustal magnetic fields did not effect the location of the bow shock but did effect the location of the MPB. The interaction between the piled-up IMF field in the MPB and the crustal magnetic fields also produced small-scale magnetic structures known as magnetocylinders, which had been observed by spacecraft (Mitchell et al 2001).…”

“…The interaction between the piled-up IMF field in the MPB and the crustal magnetic fields also produced small-scale magnetic structures known as magnetocylinders, which had been observed by spacecraft (Mitchell et al 2001). Ma et al (2002) also described the general circulation of ionospheric plasma which, in agreement simulations of Venus' plasma interaction, was upward on the day side ionosphere, day to night at higher altitudes, downward on the night side below about 250 km altitude, and down Mars magnetotail at higher altitudes. Ma et al (2004) improved on the model published in Ma et al (2002) by including a new spherical grid structure, better resolution near the inner boundary, and an additional species (CO + 2 ).…”

“…They found that an intrinsic crustal field can significantly perturb the ionosphere and the rotation of the fields may cause the large variability observed in the location of Mars' bow shock. Ma et al (2002) published the first of several three-dimensional, multi-species, singlefluid MHD studies of the interaction between Mars' exosphere and the solar wind. The first model included 3-ion species (H + , O + , and O + 2 ) and major chemical reactions, photoionization, electron impact ionization, and charge exchange interactions with Mars' extended neutral oxygen corona.…”

“…One objective was to simulate how crustal magnetic fields affect the location of the bow shock and MPB. Unlike the dipole field approximation used in Liu et al (2001), Ma et al (2002) used a crustal field modeled after spacecraft measurements of Mars' crustal field. The strongest of the magnetic fields (which occur mostly in the southern hemisphere) were placed in the sub-ram direction.…”