Description
In the solar atmosphere the catastrophic cooling phenomena known as coronal rain plays an important role in the wider context of coronal heating. Understanding coronal rain can help us put spatial and temporal constraints on the properties of the heating mechanisms. Coronal rain is observed to occur commonly above active regions as "quiescent" coronal rain, as opposed to the flare-driven kind observed in almost every flare during the gradual phase. Our current hypothesis of how quiescent coronal rain is formed is the TNE-TI (Thermal non-Equilibrium Thermal Instability) mechanism, whereby coronal loops are unable to achieve thermal equilibrium because of strongly stratified and long-lived heating, leading to plasma catastrophically cooling, condensing, and falling as coronal rain. The standard flare model proposes that the bulk of the heating in flare loops is produced by non-thermal electrons accelerated by magnetic reconnection and precipitating down to the chromosphere. However, a notable problem with this model is that it is unable to explain the formation of flare-driven rain. In this work we use 1D RHD simulations with HYDRAD and apply the TNE-TI scenario to flares to explore the existence of a secondary heating source associated with the heating. We constrain the required heating location, duration, asymmetry and volumetric heating of such additional source needed to have coronal rain whose properties match those observed.
