Influence of the tilt angle on the bow shock shape and location

Abstract

The bow shock is created in front of an obstacle immersed into a supersonic flow and its location depends on the size and shape of the obstacle. It was found that the obstacle (magnetopause) is scaled with the solar wind dynamic pressure and changes its dimensions and shape with the dipole tilt angle and interplanetary magnetic field orientation. Similar functional dependencies would be expected for the bow shock position, however, none of the bow shock models considers the parametrization of bow shock properties with the tilt angle. The present study employs a set of bow shock crossings registered during 1994–2002 by different spacecraft and demonstrates the tilt angle influence on the bow shock location. The study is based on a comparison of a recent bow shock model with observations and shows that the night–side bow shock moves in the direction of the positive ZGSM axis for positive tilt angles. The magnitude of the displacement can reach ≈3 RE. The analysis reveals that the high–latitude bow shock surface is significantly distorted near the dawn–dusk meridian. This effect was identified as a counterpart of the magnetopause indentation in the cusp region.