Modeling the Thermal Cooling Instability with CRASH*

We will present the results of one and two-dimensional (1D and 2D) simulations of the thermal cooling instability using CRASH, the University of Michigan's radiation hydrodynamics code.  We achieve conditions susceptible to the thermal cooling instability by colliding two high-speed plasma flows head-on.  The shock structure that forms between the two colliding plasma flows features two radiative shock fronts and a cold, dense post-shock region between them.  The thermal cooling instability manifests itself in the radiative shocks, which undergo temperature cycles.  We will show that these temperature cycles drive compression waves into the cold dense post-shock layer.  

In the 2D simulations, these compression waves lead to the cold dense layer fragmenting into a series of remarkable knots and filaments.  We will discuss how these knots and filaments might be diagnosed in a laboratory experiment and the challenges inherent to designing such an experiment.  This is relevant to astrophysics because the thermal cooling instability is thought to appear in a wide variety of phenomena, ranging from accretion shocks on white dwarf stars (length scale 10⁸ cm) to colliding stellar wind bubbles (length scale 10²⁰ cm).