The effects of Mach number and IMF on the location of Venus bow shock: an MHD study

Using global magnetohydrodynamics simulations, we investigate the effects of the solar wind magnetosonic Mach number and the interplanetary magnetic field (IMF) on the bow shock of Venus.  Our results reveal the following findings:  (1) The size of the Venusian bow shock is primarily determined by Mach number. An increase in Mach number results in the bow shock moving closer to Venus and a reduction in its flaring angle. (2) Both the subsolar standoff distance and the bow shock's flaring angle increase with the strength of the IMF components that are perpendicular to the solar wind flow direction (By and Bz in the VSO coordinate system), whereas the parallel IMF component (Bx) has a limited impact on the subsolar standoff distance but affects the flaring angle. (3) The cross-section of the bow shock is elongated in the direction perpendicular to the IMF on the Y-Z plane, and the elongation degree is enhanced with increasing intensities of By and Bz. (4) The quasi-parallel bow shock locates closer to the planet as compared to the quasi-perpendicular bow shock. These findings are in alignment with prior empirical and theoretical models. The influences of Mach number and IMF on the bow shock's position and geometry are attributed to the propagation of fast magnetosonic waves, showing the nature of the formation of a collisionless bow shock under the interaction of magnetized flow with an atmospheric object.