Width of the quasi-perpendicular bow shock region at Mars

¹ Department of Physics, Umeå University, 901 87 Umeå, Sweden
² Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder, USA

Received: 25 October 2023
Accepted: 16 July 2024

Abstract

Aims. We aim to quantify the width of the quasi-perpendicular Martian bow shock region to deepen the understanding of why the width is variable and which factors affect it, and to explore the implications on thermalization.

Methods. To quantify the width, 2074 quasi-perpendicular bow shock crossings from a database were studied. Upstream conditions, such as Mach numbers, dynamic pressure, ion densities, and other factors, were considered. Furthermore, the difference between the downstream and upstream temperature was measured.

Results. We found that the shock region width is correlated with the magnetosonic Mach number, the critical ratio, and the overshoot amplitude. The region was found to be anticorrelated with dynamic pressure. The width is not affected by the upstream ion density of the investigated species or by the upstream temperature. The difference between the downstream and upstream temperature is not affected by the shock region width.

Conclusions. We found that the factors that affect the stand-off distance of the bow shock, such as the magnetosonic Mach number and dynamic pressure, also affect the width. The width is also positively correlated with the overshoot amplitude, indicating that the structures are coupled or that they are affected by largely the same conditions. The lack of a correlation with the ion temperature difference indicates that the shock region width does not affect the ion thermalization.