Observations of a Twin Pair of Atypical Solar Flares and a Magnetic Reconnection Scenario

Abstract We present observations of and a magnetic reconnection scenario for a twin pair of “atypical flares” that occurred on 2022 April 22 in a quadrupolar magnetic configuration formed by two active regions. The spatiotemporal evolution of the two flares is examined using images from the Atmospheric Imaging Assembly on board the Solar Dynamics Observatory and from the ground-based Multi-Application Solar Telescope in Udaipur, India. Characteristic of atypical flares and indicative of slipping reconnection, the ribbons of each of our atypical flares: (1) do not spread apart; and (2) grow longer by the sequential brightening of new flare kernels. The two atypical flares are homologous and plausibly have homologous triggers. There are four additional pairs of flare ribbons, each from a different flaring event releasing much less energy than the atypical flares. Two of these four pairs are each made by a precursor, each possibly triggering one of the two atypical flares. The remaining two pairs accompany a filament’s activation, occurring twice within the span of the two atypical flares. Using a nonlinear force-free-field extrapolation model, we approximate the coronal magnetic field and find two quasi-separatrix layers (QSLs) that are nearly rooted in the flare ribbons of the atypical flares. The observations and the extrapolated field together suggest a scenario in which the nearly simultaneous occurrence of many reconnections between magnetic field lines crossing each other at small angles (slipping reconnection) within each of the two QSLs makes the observed pair of atypical flares.