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

TL;DR

This study investigates sequential remote brightenings during two solar flares, revealing their association with magnetic reconnection and filament material transfer, using imaging and spectroscopic data from space-based solar observatories.

Contribution

It provides the first detailed imaging and spectroscopic analysis of remote brightenings linked to interchange reconnection during successive solar flares.

Findings

Remote brightenings are caused by interchange reconnection.

Filament materials move downward with speeds up to 70 km/s.

Brightenings correspond to footpoints of closed magnetic field lines.

Abstract

Remote brightenings often appear at outskirts of source 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 H$\alpha$ Imaging Spectrograph (HIS) onboard the Chinese H$\alpha$ Solar Explorer (CHASE), which is the first space-based solar telescope of China, and 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 as visible at the H$\alpha$ red wing with a line-of-sight speed 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 caused by the heating of interchange reconnection between the erupting flux rope and closed ambient field, during which the rope-hosting filament materials are transferred to the periphery of flaring active region along the closed ambient field rather than to the interplanetary space like in the scenario of the slow solar wind formation.