What is Required Toward Reliable Data-based Solar Magnetohydrodynamic Simulations?

Data-based magnetohydrodynamic (MHD) simulations are helpful for understanding the initiation and dynamics of the solar eruptions. There are two main approaches in the data-based simulations, one is the data-constrained MHD simulation: the initial condition is taken from the observation, but the subsequent calculation of the magnetic field no longer follows the observation. The other one is the data-driven simulation in which the coronal magnetic field is driven by the time-varying photospheric magnetic field. Although the data-based MHD simulations have been conducted in recent years, there are not many discussions on the difference in results of the solar eruptions between the data-constrained and -driven simulations. In order to discuss the difference i.e., the advantages and disadvantages of them, we perform two data-based MHD simulations for the solar active region 12371 that produces an M6.5 flare. The first simulation is a full data-driven simulation where the initial condition is given by a nonlinear force-free field (NLFFF) that is extrapolated from the photosphere approximately 1 hour before the flare and then the time-varying photospheric magnetic field is imposed at the bottom surface. The second one is also a data-driven simulation, but it stops driving at the bottom before the time of flare onset and then switches to the data-constrained simulation where the horizontal magnetic field varies according to an induction equation while the normal magnetic field is fixed with time. As a result, both simulations result in an eruption, and both produce highly twisted field lines before the eruption, which is not found in the NLFFF. After the eruption, the first simulation, which is based on the time-varying photospheric field, continuously produces the sheared field lines even after the flare without reproducing the flare associated phenomena such as post-flare loops. On the other hand, the second one reproduces well the phenomena associated with flares while the evolution of the bottom magnetic field is inconsistent with the evolution of the observed magnetic field. We will analyze these results and discuss how to achieve the reliable data-based MHD simulations.