Study of reconnection dynamics and plasma relaxation in MHD simulation of a solar flare

Abstract

Self-organization in continuous systems is associated with dissipative processes. In particular, for magnetized plasmas, it is known as magnetic relaxation, where the magnetic energy is converted into heat and kinetic energy of flow through the magnetic reconnection process. An example of such a system is the solar corona, where reconnection manifests as solar transients like flares and jets. Consequently, toward investigation of plasma relaxation in solar transients, we utilize the novel approach of data-constrained MHD simulation for an observed solar flare. The selected active region NOAA 12253 hosts a GOES M1.3 class flare. The investigation of extrapolated coronal magnetic field in conjunction with the spatiotemporal evolution of flare reveals a hyperbolic flux tube (HFT), overlying the observed brightenings. MHD simulation is carried out with the EULAG-MHD numerical model to explore reconnection dynamics. Three distinct sub-volumes are chosen and are subjected to analysis of magnetic field line dynamics along with time evolution of various physically relevant quantities like magnetic energy, current density, and twist. The overall simplification of field line complexity in each sub-volume, decay of magnetic energy and current density because of reconnection are found to be the prime signatures of relaxation. The size and position of chosen sub-volumes with respect to the boundaries of computational box are seen to play an important role in governing the overall dynamics. The terminal state of simulation for all the sub-volumes is checked for the well known Taylor(1974) predicted state of a linear force-free field configuration and we found the results to be not consistent with a linear force-free field. We think that the resolution, efficiency of reconnection in the simulation, and assumptions regarding selection of sub-volumes may have a bearing on the results, which we aim to explore in future works.