Investigation of radiative bow-shocks in magnetically accelerated plasma flows.

We present a study of the formation of bow shocks in radiatively cooled plasma flows. This work uses an inverse wire array to provide a quasi-uniform, large scale hydrodynamic flow accelerated by Lorentz forces to supersonic velocities. This flow impacts a stationary object placed in its path, forming a well-defined Mach cone. Interferogram data are used to determine a Mach number of ~6, which may increase with radial position suggesting a strongly cooling flow. Self-emission imaging shows the formation of a thin (<60 µm) strongly emitting shock region, where Te ~ 40-50 eV, and rapid cooling behind the shock. Emission is observed upstream of the shock position which appears consistent with a radiation driven phenomenon. Data are compared to 2-dimensional simulations using the Gorgon MHD code, which show good agreement with the experiments. The simulations are also used to investigate the effect of magnetic field in the target, demonstrating that the bow-shocks have a high plasma ß, and the influence of B-field at the shock is small. This consistent with experimental measurement with micro bdot probes. [ABSTRACT FROM AUTHOR]