Subcritical Shock Structure in a Highly Collisional Plasma*

Shock interactions are common in astrophysical systems, for example HH objects in protostellar jets. We present results from a laboratory study of interacting bow shocks in magnetised collisional HED plasmas. Shocks are produced by placing cylindrical obstacles into the supersonic, super-Alfvénic outflow from an inverse wire array z-pinch at the MAGPIE pulsed power facility. Magnetic field pile-up at the obstacles leads to the formation of subcritical bow shocks which are supported by downstream magnetic pressure. Optical Thomson scattering measurements show that the flow remains supersonic across the subcritical shocks and hydrodynamic-like shocks are seen in the downstream. We compare experiments with multiple obstacles both with and without magnetic field pile-up and discuss the differences in shock interaction geometry. New measurements of the magnetic field by Faraday rotation imaging confirm the importance of magnetic field compression. Radiative MHD simulations show good agreement with the experimental results, paving the way for MHD simulations of astrophysical shock reflection which include a magnetic field.