The Nature of Solar Flare Reconnection

Solar flares are among the most energetic events in the solar system, capable of releasing over 10^32 ergs in the forms of heating, energetic particles, and bulk motion. This energy release is known to be driven by magnetic reconnection, a plasma process that explosively releases stored magnetic energy through a rearrangement of the magnetic topology. Determining the structure and dynamics of flare reconnection is therefore essential for modeling and predicting the energy release channels of these events. Whereas direct observation of the reconnection dynamics is difficult, detailed constraints on the dynamics can be obtained from the “flare ribbons” that track the chromospheric footpoints of newly reconnected field lines and the “flare loops” of very hot (>10MK) plasma that illuminate the reconnected magnetic structures. We present a new high-resolution, three-dimensional magnetohydrodynamics model of a solar flare performed with the ARMS code. In our model, the flare ribbons exhibit characteristic ‘whorls’ that represent indirect evidence of reconnection-generated structures known as plasmoids that are thought to be important for particle acceleration. We furthermore show that the orientation of the flare loops reveals important information about the so-called ‘guide magnetic field’ thought to play a critical role in plasmoid structure and associated particle acceleration efficiency. We discuss implications for understanding how, when, and where solar flares accelerate particles.