Relationship between Flare Kernels in Hα Far‐Blue Wing and Magnetic Fields

Abstract

Big Bear Solar Observatory (BBSO) recently developed fast camera systems to observe solar flares with subsecond cadence. In most of our observations, we observed at Hα-1.3 Å to study the chromospheric emission from flare kernels, which are usually regarded as being associated to nonthermal electron precipitation. For all four flares in Active Region 8674 that we analyzed, we compared the initial brightening of flare kernels at this wavelength with photospheric magnetograms and found that initial brightenings avoided strong line-of-sight magnetic regions; importantly, all nine flare kernels were within 10,000 km of magnetic neutral lines. The observed flare morphology and evolution suggest that emission near a magnetic neutral line may come from unresolved footpoints of interacting flare loops, where nonthermal electrons were precipitated, or from a low-lying compact loop due to instantaneous heating in the early phase of the flare. Our current observations cannot distinguish between these two mechanisms. It is suggested that impulsive compact flares involve low-lying magnetic loops or magnetic reconnection at small altitudes in contrast to eruptive long-duration flares.