Solar wind interaction with the Earth's magnetic field: 2. Magnetohydrodynamic bow shock

The earth's bow shock has been investigated as a magnetohydrodynamic discontinuity using the plasma and magnetic data supplied 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 γ1 = 1.75 or 2.25 depending on the presence or absence of upstream waves. Computations of the shock velocity performed for 23 crossings gave an average speed of ∼85 km/sec.