A model of the Earth's distant bow shock

Abstract

We present a new global model of the Earth's bow shock that is parametrized by the solar wind conditions. We begin with a conic section base model taken to be correct for average solar wind conditions. Then we apply modifications to the base model, based on physical arguments, to account for the changes in the size and shape of the bow shock caused by changes in the prevailing solar wind dynamic pressure, Alfvén and sonic Mach numbers, and interplanetary magnetic field orientation. We show that our model matches the location and timing of shock crossings observed, at large downtail distances, by the Galileo spacecraft during December 1990 and December 1992 and by the Pioneer 7 spacecraft during September 1966. Magnetic field and plasma moments in a shock normal coordinate system change across the model shock surface as required by conservation laws.