Modeling Observable Differences in Flare Loop Evolution due to Reconnection Location and Current Sheet Structure
Longcope, Dana W.
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Flare reconnection is expected to occur at some point within a large-scale coronal current sheet. The structure of the magnetic field outside this sheet is almost certain to affect the flare, especially its energy release. Different models for reconnection have invoked different structures for the current sheet's magnetic field and different locations for the reconnection electric field within it. Models invoking Petschek-type reconnection often use a uniform field. Others invoke a field bounded by two Y-points with a field strength maximum between them and propose this maximum as the site of the reconnection electric field. Still other models, such as the collapsing trap model, require that the field strength peak at or near the edge of the current sheet and propose that reconnection occurs above this peak. At present there is no agreement as to where reconnection might occur within a global current sheet. We study the post-reconnection dynamics under all these scenarios, seeking potentially observable differences between them. We find that reconnection occurring above the point of strongest field leads to the highest density and the highest emission measure of the hottest material. This scenario offers a possible explanation of superhot coronal sources seen in some flares.
Unverferth, John, and Dana Longcope. “Modeling Observable Differences in Flare Loop Evolution Due to Reconnection Location and Current Sheet Structure.” The Astrophysical Journal 894, no. 2 (May 18, 2020): 148. doi:10.3847/1538-4357/ab88cf.