Sequential Remote Brightenings and Co-spatial Fast Downflows during Two Successive Flares

Abstract

Remote brightenings often appear at the outskirts of the active regions of solar eruptive events. Nevertheless, their origin remains to be ascertained. In this study, we report imaging and spectroscopic observations of sequential remote brightenings with a combination of observations from the Hα Imaging Spectrograph on board the Chinese Hα Solar Explorer, which is the first space-based solar telescope of China, and from the Solar Dynamics Observatory. It is found that during two successive M-class flares occurring on 2022 August 17 multiple ribbon-like brightenings appeared in sequence away from the flaring active region. Meanwhile, abundant cool filament materials moved downward to the sequential remote brightenings, which were visible at the Hα red wing with a line-of-sight speed of up to 70 km s−1. The extrapolated three-dimensional magnetic field configuration shows that the sequential remote brightenings correspond to the footpoints of closed ambient field lines whose conjugate footpoints are rooted in the main flare site. We suggest that the sequential remote brightenings are most likely to be caused by the heating of the interchange reconnection between the erupting flux rope and the closed ambient field, during which the rope-hosting filament materials are transferred to the periphery of the flaring active region along the closed ambient field rather than to the interplanetary space, such as in the scenario of slow solar wind formation.