Laboratory study of high- plasma shock waves

Abstract

A plasma wind tunnel has been used to generate shock waves at rest in the laboratory reference frame. The upstream pressure ratio beta is in the range 1-3, and the Mach number based on the fast magnetosonic wave speed is 3 to 5. The shock wave is formed by letting the plasma 'wind' impinge on the field of a magnetic obstacle. The resulting shock is primarily transverse, and exhibits a thickness of 0.8 to 1.2 times the ion inertial length c/ omega pi. The shock thickness decreases with increasing Mach number, and increases as the ion mass is increased. Measured values of upstream and downstream magnetic field particle density, and temperature agree with those calculated from the shock conservation relations. Magnetic fluctuations in the shock front are observed, with frequencies near the ion cyclotron frequency. Comparisons of these results with those of other experiments, and with the Earth's bow shock, are made.