Multiple Extreme Ultraviolet Peaks Attributed to Three-dimensional Magnetic Reconnection in a Long-duration Solar Flare

TL;DR

This study investigates a long-duration solar flare with multiple EUV peaks, attributing them to different 3D magnetic reconnections driven by flux rope evolution, linking observations with magnetic structures and flare dynamics.

Contribution

It provides the first detailed explanation of multiple EUV peaks in a long-duration flare as resulting from distinct 3D magnetic reconnections involving flux ropes.

Findings

Multiple EUV peaks correspond to different 3D magnetic reconnections.

Reconnection processes involve flux rope and ambient field interactions.

Results connect EUV light curves with magnetic structures and CME evolution.

Abstract

Solar flares are a major driver of hazardous space weather, whose intense electromagnetic emissions and energetic particles can significantly disturb the near-Earth space environment. Therefore, understanding the physical processes during a solar flare and predicting its radiation profiles are of great importance. In this study, we analyze and model an M1.4 two-ribbon long-duration flare, whose multiple extreme-ultraviolet (EUV) emission peaks are found to correspond to different three-dimensional (3D) magnetic reconnections driven by the continuous evolution of a flux rope. In particular, the second and third peaks in the 335 {\AA} EUV channel originate from longer and higher flare loops with extended cooling times, formed by reconnection between flux-rope field lines and ambient sheared-arcade field lines ($ar\text{--}rf$) and between flux-rope field lines themselves ($rr\text{--}rf$). These results are supported by the drifting of the flux-rope footpoint (and flare ribbon) and the decrease in toroidal flux of the flux rope, as well as by the connectivity transfer of representative field lines in the magnetohydrodynamic (MHD) simulation. This work points out, for the first time, new manifestations of the 3D flare scenario in EUV light curves. On the one hand, it provides an explanation for two-ribbon late-phase flares. On the other hand, the conclusions presented here help bridge the gap between imaging observations, EUV light-curve diagnostics, and the magnetic structures of the associated coronal mass ejections.