A summary of observations of the earth's bow shock

The earth's bow shock can be regarded as a fast steady-state collisionless magnetohydrodynamic shock exhibiting a wide range of plasma parameter values or as an example of superalfvenic flow of a MHD fluid past a blunt body. This paper summarizes our knowledge of the bow shock. Satellite crossings of the shock have given some empirical data on the position and shape of the bow shock. Theoretical calculations on position and shape show the critical nature of the Alfven number. The main physical process to be explained with regard to the bow shock is the mechanism of thermalization of the upstream solar wind. Some of the main classes of shocks observed are quasi-parallel shocks, low Mach number laminar shocks, and high beta shocks.