SPONTANEOUS CURRENT-LAYER FRAGMENTATION AND CASCADING RECONNECTION IN SOLAR FLARES. II. RELATION TO OBSERVATIONS

In a paper by Barta et al., the authors addressed by means of high-resolution MHD simulations some open questions on the CSHKP scenario of solar flares. In particular, they focused on the problem of energy transfer from large to small scales in the decaying flare current sheet (CS). Their calculations suggest that magnetic flux ropes (plasmoids) are formed in a full range of scales by a cascade of tearing and coalescence processes. Consequently, the initially thick current layer becomes highly fragmented. Thus, the tearing and coalescence cascade can cause an effective energy transfer across the scales. In this paper, we investigate whether this mechanism actually applies in solar flares. We extend the MHD simulation by deriving model-specific features that can be searched for in observations. The results of the underlying MHD model show that the plasmoid cascade creates a specific hierarchical distribution of non-ideal/acceleration regions embedded in the CS. We therefore focus on the features associated with the fluxes of energetic particles, in particular on the structure and dynamics of emission regions in flare ribbons. We assume that the structure and dynamics of diffusion regions embedded in the CS imprint themselves into the structure and dynamics of flare-ribbon kernels by means of magnetic field mapping. Using the results of the underlying MHD simulation, we derive the expected structure of ribbon emission and extract selected statistical properties of the modeled bright kernels. Comparing the predicted emission and its properties with the observed ones, we obtain a good agreement between the two.