Pulse-beam heating of deep atmospheric layers, their oscillations and shocks modulating the flare reconnection

Abstract

Aims. We study the processes occurring after a sudden heating of deep atmospheric layers at the flare arcade footpoints, which is assumed to be caused by particle beams. Methods. For the numerical simulations we adopt a 2D magnetohydrodynamic (MHD) model, in which we solve a full set of the time-dependent MHD equations by means of the FLASH code, using the adaptive mesh refinement (AMR) method. Results. In the initial state we consider a model of the solar atmosphere with densities according to the VAL-C model and the magnetic field arcade having the X-point structure above, where the magnetic reconnection is assumed. We found that the sudden pulse-beam heating of deep atmospheric layers at the flare arcade footpoints generates two magnetohydrodynamic shocks, one propagating upwards and the second propagating downwards in the solar atmosphere. The downward-moving shock is reflected at deep and dense atmospheric layers and triggers oscillations of these layers. The period of these oscillations in our case is about 174 s. These oscillations generate the upward-moving magnetohydrodynamic waves that can influence the flare magnetic reconnection in a quasi-periodic way. These processes require a sudden heating in very localized regions in dense atmospheric layers; therefore, they can be also associated with seismic waves.