Beam-driven evaporation in 2.5D flare simulations with an asymmetric magnetic field configuration

The standard flare model is often depicted and studied starting from a perfectly antisymmetric magnetic field configuration with left−right symmetry in magnitude, on either side of the polarity inversion line. However, flare observations confirm that most flares have a significantly asymmetric magnetic field across the inversion line. To study asymmetric flare evolutions in both thermal and nonthermal components, self-consistent multidimensional models must incorporate nonlocal, beam-driven feedback on the stratified, thermal plasma. Here we present the first multidimensional magnetohydrodynamic flare simulation featuring evaporation driven by energetic electron beams that has an asymmetric background magnetic field configuration. The entire flare evolution depends significantly on those electron beams as they drive the evaporated plasma upward from the lower atmosphere. We study the impact of an asymmetric configuration on the evolution and geometry of a self-consistent, beam-driven flare loop system using the MPI-AMRVAC toolkit. We contrast the typical left−right symmetric case with the more realistic asymmetric setup. We observe the formation of a rotating flux rope, as well as an asymmetric behavior in the strength of hard X-ray (HXR) fluxes, and discuss the influence on the chromospheric evaporation at either footpoint. In line with the latest observational findings, our models display distinct spatiotemporal variation in the HXR emission and flare ribbon evolutions. In particular, we discuss how our model exhibits both the Sakao effect, where local field strength would anticorrelate with HXR source strengths, and the anti-Sakao effect, where local field strength would correlate with HXR source strengths, in the same simulation.