Magnetic field overshoots in the Martian bow shock

Abstract

In 1989 the Phobos 2 spacecraft provided sufficient plasma and magnetic field data for statistical investigations of the Martian bow shock structure. Significant magnetic field overshoots were observed in more than 70% of the bow shock crossings detected in the terminator region. According to our studies based on the available low‐resolution data set, the features of the Martian overshoots are very similar to those observed in the terrestrial and Venusian bow shock: the magnitude increases with increasing Mach number and the thickness scales as the proton gyroradius computed from the upstream solar wind speed and magnetic field strength. Our investigations seem to support the idea of Mellott and Livesey [1987] suggesting that overshoots may develop not only in supercritical shocks but also when the Mach number is below or around the critical value.