Three-dimensional MHD Simulations of the Magnetic Pileup at Mars

Abstract

In this study, we introduced a quantitative parameter, the magnetic field strength difference, to denote the intensity of the magnetic pileup effect at Mars. Using a three-dimensional multispecies MHD model, the effects of the interplanetary magnetic field (IMF) and the solar wind dynamic pressure ( P _d ) constituted with different densities and velocities on the magnetic pileup were examined. Our results show that: (1) the magnetic pileup at Mars mainly occurs at the dayside region and its magnitude is generally decreasing with increasing solar zenith angle. The magnetic pileup is generally weak in the intense crustal field region, while it is strong in the weak crustal field region. (2) The perpendicular IMF components, B _Y and B _Z , dominate the magnetic pileup, while the radial IMF component, B _X , has little effect. In the intense crustal field region, when the IMF and crustal field are primarily in the same direction, the magnetic field is piled up and the pileup magnitude is generally strong. While the directions of the crustal field and IMF are opposite, the occurrence of magnetic reconnection can weaken the local magnetic pileup. (3) Under the same P _d , a higher solar wind velocity results in a higher intensity and a larger region of the magnetic pileup. When P _d increases, the magnitude of the magnetic pileup is enhanced, but the pileup region shrinks. In addition, for an increasing P _d , at the center of the induced magnetotail, the asymmetric current sheet can lead to similar asymmetries of the pileup.

Keywords

• Interplanetary magnetic fields
• Planetary magnetospheres
• Mars
• Solar wind