The Mach number is one of the most important parameters of collisionless shocks. The accuracy of its observational determination is compromised by several complications. Incomplete measurements of plasma parameters significantly contribute to the uncertainty, along with the errors of the normal determination. A set of CLUSTER observed shocks is analyzed using several methods for finding the shock normal and to circumvent the shortcomings of the plasma data. A relation between the maximum magnetic compression and the Alfvénic Mach number is established. It is proposed as a proxy for the Mach number estimate when measurements are incomplete.
Gedalin, M., Russell, C. T., Dimmock, A. P. (2021). Shock Mach number estimates using incomplete measurements. Journal of Geophysical Research: Space Physics, 126, doi: 10.1029/2021JA029519
License: CC BY-NC-ND 4.0