Quantitative shadowgraphy of density structures in radiative magnetic reconnection experiments

We present updated results from magnetic reconnection experiments with both strong radiative cooling and the plasmoid instability. These two plasma processes are present in many astrophysical environments, such as the interstellar medium, solar chromosphere, and black hole accretion disks. To study the key physics of astrophysically-relevant reconnection, the MARZ (Magnetic Reconnection on Z) collaboration drives dual exploding aluminum wire arrays on Sandia's Z Machine. In three separate MARZ experiments, the spacing between the two arrays was shifted; in changing the inflow parameters (velocity, density, field), we vary the reconnection layer formation and evolution. The key diagnostic tracking the time-varying layer structure is laser shadowgraphy. Qualitatively, the experimental shadowgrams share image features with ray-traced simulations: a dense layer with temporally-increasing density gradients due to radiative collapse; standing MHD shocks outside the layer; instabilities along the axial direction consistent with plasmoids. Quantitatively, the shadowgraphy intensity profiles from experiment are reproduced by ray-tracing a simple analytic Gaussian model layer. This forward model estimates the characteristic density jump and width of the reconnection layer.