Exploring Magnetic Reconnection in a Sub-A-class Microflare Using Data-constrained Numerical Simulation and Multi-instrument Observations

Abstract Solar flares are intermittent events that convert free magnetic energy into heat and kinetic energy of charged particles, along with a rearrangement of magnetic field lines (MFLs) through magnetic reconnection. This work investigates an active-region sub-A-class microflare detected by the Solar X-ray Monitor on board Chandrayaan-2. The MFL topology, its evolution, and the associated magnetic reconnection in the flaring region are investigated. The coronal magnetic field is constructed using the nonlinear force-free field (NLFFF) extrapolation model, indicating the presence of a magnetic flux rope (MFR) at the flaring location. Notably, this MFR exhibits regions of high magnetic field gradient and a nonuniform distribution of twist along its axis. Furthermore, the dynamics of the MFR is explored using a three-dimensional data-constrained magnetohydrodynamics simulation performed using the EULAG-MHD code. The simulation shows overall untangling of the MFLs that constitute the MFR, along with changes in their connectivity, which suggests underlying magnetic reconnection. Further, a few representative MFLs belonging to the MFR over a given time span are advected with the plasma flow to maintain their identity. These field lines show a change in connectivity, and such reconnections can contribute to the unfurling of the MFR. The overall scenario is generally consistent with the concept of braiding reconnection in an MFR.