The Nature of Solar Flare Reconnection

Abstract:

Solar flares are explosive space weather events that can, in the span of only a few minutes, release well over 10^32 ergs of energy in the forms of plasma heating, energetic particles, and bulk motion. Flares are known to be driven by magnetic reconnection; consequently, determining the structure and dynamics of flare reconnection is essential for modeling and eventually predicting the energy release channels of these events. In particular, the amount of energy that ends up as energetic particles is believed to be highly dependent on whether the reconnection is primarily turbulent or primarily laminar. We use the well-proven adaptive mesh refinement capabilities of the ARMS MHD code to perform new very-high-resolution simulations of three-dimensional reconnection in an eruptive flare and compare the results to recent data. Although flare reconnection is difficult to observe directly in the corona, highly detailed constraints on its dynamics can be obtained from observations of the so-called flare ribbons that track the chromospheric footpoints of newly reconnected field lines. The analogues of flare ribbons in our simulations are identified by tracking discontinuous changes in field-line magnetic connectivity due to the reconnection. We discuss the implications of the simulated ribbon formation for the nature of flare reconnection. We also determine how the time-evolving guide field in flares affects the formation of the ribbons and, hence, the reconnection dynamics. We interpret our results through an analytical model, and discuss implications for SDO, IRIS, and GST observations of explosive flare energy release.

This work was supported in part by the SolFER DRIVE Center and by the NASA LWS Program.