Solar wind interaction with the earth's magnetic field : II) The Magnetodydrodynamic bow shock

The Earth's bow shock has been investigated as a magnetodydrodynamic discontinuity using the plasma and magnetic data supllied by the European satellite HEOS-1. The jumps of the fluid parameters through the shock have been studied, as a function of the Mach number and of the geometry of the shock surface. The solar wind specific heat ratio has been found to be gamma2 = 1.75 or 2.25 depending on the presence or absence of upstream waves.Computations of the shock velocity, performed for 23 crossing, gave an average speed of ~85 km/sec.