The Topology of Magnetic Reconnection in Solar Flares

8this 2D standard flare model. Also, the footpoint separation velocity predicted in the standardmodel is a only few km s −1 (Somov et al., 1998). Actual observed apparent velocitiesare much larger, on the order of 50 km s −1 . To account for the observed directions andspeeds of HXR footpoint sources, and thus the evolution of reconnection, a 3D model isneeded.Flare Energy StorageAfter the standard model for the release of energy in a solar flare was developed, thenext question became how so much energy is made available to fuel a flare. Current evidencepoints to the build-up of energy over days as the photospheric magnetic field shiftscontinuously prior to a flare. Changes in the field at the photospheric boundary (almostcertainly driven by sub-photospheric phenomona) drive the chromospheric and coronalplasma. The coronal field may remain nearly potential (current-free), but accumulates anon-potential component related to current layers that separate interacting magnetic fluxesand thus prevent coronal flux changes (Henoux and Somov, 1987). In other words, energyis stored in the corona due to changes in the photospheric boundary because no reconnectiontakes place and the magnetic configuration becomes stressed. The field becomes moreand more non-potential until some critical point is reached and a flare occurs.Past research on energy storage prior to a flare has concentrated on non-potential signaturesin the photospheric fields as observed by vector magnetograms (i.e.Gary et al.,1987; Wang et al., 1996; Moon et al., 2000; Deng et al., 2001; Tian et al., 2002; Falconeret al., 2006; Dun et al., 2007). These yield maps of not only the magnitude of the field butalso the its direction. For example, Dun et al. (2007) calculated the daily average valuesof three non-potential parameters from vector magnetograms of selected regions along themain neutral lines of active region 10486. They found that the three non-potentiality parametersincreased at the impulsively brightening flare sites from values measured at least