Effects of the interplanetary magnetic field clock angle on the shape of bow shock

Abstract

Using the global magnetohydrodynamics (MHD) simulation model, we investigated the effects of the interplanetary magnetic field (IMF) clock angle on the shape of bow shock, including its rotational asymmetry and subsolar point. For general northward IMF (z component B z > 0), the rotational symmetry of the bow shock is broken by the effects of fast magnetosonic Mach number (M ms), and the cross-sectional line of the bow shock is an ellipse with the semi-major axis along the direction perpendicular to the IMF. The ratio or D-value between semi-major and semi-minor axis can be used to illustrate the extent of asymmetry of the bow shock. On the basis of the multiple parameters fitting, we obtain the changing relationship of both semi-axes with the clock angle and the distance away from the Earth. For general southward IMF (B z 0, and decreases with the increasing IMF clock angle for B z < 0.