# Abstract

 PROXY PARAMETER FOR THE MACH NUMBER

 J. Pipaliya, The University of Sheffield, jivraj@hotmail.co.uk

 One of the key aspects of the in-situ measurements of collisionless shocks is ability to identify basic shock parameters such as Mach number $(M)$, angle $(\theta_{Bn})$ between the upstream magnetic field and the normal to the shock front. However, for some planetary missions, the comprehensive plasma data that allow us to identify the upstream density and velocity (required for the identification of the Mach number) are not available. In the present study, which is based on the analysis of Cluster data, we have developed a statistical relation between change of the magnetic field in the ramp of the quasi-perpendicular shock, $(\theta_{Bn})$ and Mach number $(M)$. It is argued that this statistical relation can be used as a proxy for the Mach number parameter if plasma data are not available.