Current sheet formation under radiative cooling

Abstract

We present a simple, analytically solvable MHD model of current sheet formation through X-point collapse under optically thin radiative cooling. Our results show that cooling accelerates the collapse of the X-point along the inflows, but strong cooling can arrest or even reverse the current sheet elongation in the outflow direction. Hence, we detail a modification to the radiatively-cooled Sweet-Parker model developed by Uzdensky & McKinney (2011) to allow for varying current sheet length. The steady-state solution shows that when radiative cooling dominates compressional heating, the current sheet length is shorter than the system size, with an increased reconnection rate compared to the classical Sweet-Parker rate. The model and subsequent results lay out the groundwork for a more complete theoretical understanding of magnetic reconnection in regimes dominated by optically thin radiative cooling.