Dartmouth Events

Abstract:

Solar flares are explosive space weather events that rapidly convert stored magnetic energy into bulk motion, plasma heating, and particle acceleration via magnetic reconnection. Recent theory and modeling have demonstrated the importance of plasmoid structures, as well as the strength of the reconnection guide field, in controlling the efficiency of the nonthermal particle acceleration. While direct observation of the magnetic field dynamics in the corona is highly challenging, key insights can be derived from the so-called ‘flare ribbons’ where flare-energized particle beams illuminate the footpoints of reconnected magnetic fields, and ‘flare loops’, the highly EUV-emissive magnetic structures formed by reconnected magnetic fields. We present new high-resolution MHD simulations of three-dimensional reconnection in an eruptive flare and compare to recent data. We derive analogues of flare ribbon and show that they are highly structured and exhibit many ‘whorl’ patterns that are linked to turbulent plasmoids in the reconnecting current sheet. Such flare ribbon fine structure reveals crucial information about the fundamental turbulent vs. laminar nature of the reconnection. We also show that the guide field weakens more than an order of magnitude over the course of the flare, and instantaneously varies over a similar range along the three-dimensional current sheet. We demonstrate how the guide field may be inferred from observations of sheared post-flare loops. Interestingly, we find that the number of plasmoids in the flare reconnecting current sheet increases with weakening guide field, underscoring the important role of the guide field in particle acceleration. We discuss the implications for understanding particle acceleration and explosive energy release in solar flares and throughout the universe.

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https://dartmouth.zoom.us/j/92751420885?pwd=QnIwN0RiSGkzMUtjQVZxRlZLMkcwQT09

Meeting ID: 927 5142 0885
Passcode: Plasma