On the onset of a flare through MHD simulation initialized with non-force-free-field extrapolation

A solar flare is one of the most explosive phenomena in the solar atmosphere. Though magnetic reconnection is believed to be the major cause behind this energetic phenomenon which can explain the process of energy released, the onset, ongoing mechanism during the flaring process, the released energy process, and afterward impact on the surrounding atmosphere are still intriguing. Here we have studied one eruptive flare to understand the onset and the physical properties of magnetic reconnection. We investigated the M1.1 flare on May 23, 2021, peaking at ~11:08 UT in NOAA AR 12824 by a data-constrained MHD simulation initiated with a novel non-force-free-field (NFFF) extrapolation model. In the extrapolated field, we obtained the initial magnetic field configuration near the flaring region. We found one flux rope, a three-dimensional magnetic null point, and a set of sheared arcade-type field lines spanning over the flare. We then performed an MHD simulation using the EULAG-MHD (Eulag/semiLagrangian fluid solver) model to understand the evolution of different topologies during the flaring activity with an open and line-tied boundary condition utilizing the NFFF extrapolated magnetic field as initial condition. The simulation is first driven by only the inherent non-zero Lorentz force exhibited in the extrapolated field and later it develops the plasma flow. Noteworthy is their remarkable correspondence to the observational features seen in multiwavelength channels of AIA/SDO. Additionally, we have estimated the reconnection flux using the flare ribbons from observations. A similar approach is adopted in the time-dependent evolution, where we have calculated the fluxes using a set of sample field lines passing through the ribbon area. Interesting is their quantitative agreement with each other. Within the scope of the simulation, we have attempted to calculate the (approximated) reconnection rate during the flaring process using the sample field lines used for the estimation of reconnection fluxes. Also, we followed the method in Isobe et al (2002) for our calculation of the reconnection rate (M_A) and found the value of M_A smaller than their range.