The onset of magnetic reconnection in dynamically evolving coronal current sheets

The problem of the onset of reconnection in the solar corona is a nuanced one. Release of magnetic energy via reconnection cannot be ubiquitous and efficient, or not enough energy would build up to drive the observed heating and explosive events in the corona. However, deriving criteria for rapid onset is not trivial. Here we focus on two parameters of coronal current sheets thought to be responsible for nanoflare heating of the corona: thickness and the strength of the reconnecting component (sometimes called ‘shear’). We present results of simulations of the onset of magnetic reconnection in dynamically thinning current sheets applicable to coronal current sheets. We find that onset occurs when tearing instability growth timescales become smaller than the system dynamical timescale (thinning time), and that the onset of reconnection follows a similar storyline as in previous studies of static sheets, which allows for predictions of onset criteria to be developed.