Investigating the Formation and Dynamics of Magnetic Islands in Radiatively-Cooled Reconnection

Radiatively-cooled magnetic reconnection has been hypothesized to be responsible for many dynamic phenomena in extreme astrophysical environments such as coronal heating in compact accretion disks and the high energy gamma-ray flares observed in pulsar wind nebulae. Previous theoretical work by Uzdensky and McKinney [PoP, 2011] identifies compressibility to be a crucial modification to their version of the Sweet-Parker model in the radiatively cooled regime. However, this model does not include the effects of tearing and plasmoid formation which serve as a trigger for fast reconnection. Alternatively, work by Steinholfsen, Van Hoven and Tachi [ApJ, 1984] characterizes the interaction between radiation and the tearing instability for an incompressible plasma. Our simulations of radiatively-cooled reconnection driven by pulsed power [JPP 2024] show that the formed plasmoids undergo radiative collapse before ejection through the outflows. This motivates the presented work, which aims to study the interaction of optically thin radiation and tearing to characterize the growth and collapse of magnetic islands in the radiatively-cooled regime. This includes analytic work on linear and non-linear tearing in a compressible plasma, supported by 2D MHD simulations using Athena ++ of a double current sheet cooled by Bremsstrahlung radiation. The numerical work is extended to include other astrophysically relevant cooling processes such as Synchrotron and Inverse-Compton cooling.