Resistive diffusion and radiative cooling effects in magnetized oblique shocks

TL;DR

This study investigates magnetized oblique shocks in plasmas, demonstrating how resistive diffusion and radiative cooling influence shock structure and behavior through experiments on a pulsed power facility.

Contribution

It provides the first experimental analysis of perpendicular-type oblique shocks considering both resistive diffusion and radiative cooling effects.

Findings

Shocks show shallower angles and higher density compression than Rankine-Hugoniot predictions.

Experimental results align with a model including resistive diffusion and radiative cooling.

Oblique shocks can support magnetic field compression in plasma systems.

Abstract

Magnetized oblique shocks are of interest in various plasmas, including in astrophysical systems, magneto-inertial confinement fusion experiments, and in aerospace applications. Through experiments on the COBRA pulsed power facility (Cornell University, 1~MA peak current, 100~ns rise time), we investigate oblique shock formation in a system with a magnetic field, and where both radiative cooling and resistive diffusion are important. Compared to previous pulsed power experiments, which have investigated quasi-parallel oblique shocks, here we consider perpendicular-type shocks, which can support magnetic field compression. In our experiments, supersonic, super-Alfv\'enic, collisional plasma flows, generated using an aluminum exploding wire array, are deflected by angled obstacles to generate oblique shocks. The shocks are imaged using laser shadowgraphy and Mach-Zehnder interferometry, while optical Thomson scattering provides measurements of the flow velocity and temperature. The shocks exhibit shallower shock angles and higher density compression, when compared to canonical Rankine-Hugoniot predictions. These results are best described by a model that includes both resistive diffusion and radiative cooling, consistent with the values of the cooling parameter and the resistive diffusion length in the experiment.