Modelling radiative collapse in high energy density systems using static mesh refinement

Radiative collapse occurs in dense plasmas where radiative loss drops the thermal pressure below the compressional magnetic pressure, leading to a runaway collapse to very small scale lengths. This is hypothesised to occur in the reconnection layer formed between two adjacent exploding wire arrays, driven by strong currents from Z facility at Sandia National Laboratories. In this regime, the reconnection layer can reach high enough densities and temperatures to radiatively cool and ultimately collapse to a very small region.

To simulate the above system, it is critical to capture the dynamics of both the reconnection layer (of spatial order 100um) and the wire arrays (of order 10cm across). Resolving features with at least three orders of magnitude difference is intractable on a uniform simulation grid, and requires a mesh refinement capability, such as that newly implemented in the radiation-MHD code, Chimera. Using this capability, it is found that the plasmoid instability typically observed in the reconnection layer simulations is sensitive to cell resolution, 3D effects and radiation treatment. This talk investigates the balance between achieving sufficient resolution to capture plasmoids formation, and both 3D effects and radiative cooling disrupting the onset of this instability.