Numerical schemes and dissipative processes in three-dimensional modeling of post-flare loops and their EUV signatures

Abstract

Solar flares release magnetic energy into the solar corona and drive the formation of hot post-flare loops, but their thermodynamic evolution depends on both the physical processes included in the model and the numerical scheme used to solve the magnetohydrodynamic (MHD) equations. We investigate the formation and evolution of post-flare loops using three-dimensional non-ideal MHD simulations that include magnetic resistivity, optically thin radiative losses, anisotropic thermal conduction, and coronal heating. Our objectives are to quantify how numerical schemes affect energy dissipation, determine the thermodynamic role of the main dissipative processes, and produce synthetic extreme-ultraviolet (EUV) emission maps and light curves. We carried out nine simulations and found that the choice of Riemann solver impacts flare energetics. Among the five approximate solvers considered, HLLD shows the least diffusive behavior in the present setup and produces energy partitions closest to those obtained with the Roe reference solution, whereas HLL and HLLE are substantially more diffusive. Coronal heating and optically thin radiative losses modify the energy balance. In particular, radiative losses reduce the fraction of released magnetic energy retained as internal energy, preventing unrealistically high coronal temperatures. Anisotropic thermal conduction efficiently redistributes energy along magnetic field lines and smooths the thermal and density structure of post-flare loops. Synthetic emission maps in the SDO/AIA 94 Å and 131 Å channels reproduce the main morphological properties of post-flare loops, while the corresponding light curves and flux ratios provide quantitative diagnostics of the temporal evolution of the EUV emission and the thermal properties of the flare arcade. These results show that a reliable physical interpretation of three-dimensional flare simulations requires careful consideration of both the adopted numerical scheme and the dissipative processes included in the model.