2026/04/07 by Hanya Pan, Astrid Veronig, Rui Liu +2 · 1 voice
Physics and Astronomy · #Astrophysics and Cosmic Phenomena #Ionosphere and magnetosphere dynamics #Solar and Space Plasma Dynamics
paper · doi:10.3847/1538-4357/ae5183
openalex publication_date 2026/04/07 · openalex created_date 2026/04/08 · openalex updated_date 2026/07/22
Abstract Supra-arcade downflows (SADs)—dark, tadpole-like, sunward-moving structures observed above post-flare loops—are considered key signatures of magnetic reconnection in solar eruptions. However, their physical origin and connection to reconnection dynamics remain controversial. In particular, their connection to hard X-ray (HXR) emission has been elusive, as they are predominantly observed during the flare decay phase. In this study, we investigate SADs that occurred during the late decay phase of a long-duration M6.7 flare on 2022 August 22 and their relationship with HXR emission, observed by the Solar Dynamics Observatory and Solar Orbiter. While thermal HXR emission dominates most of the decay phase, a significant nonthermal HXR enhancement with an electron power-law index of δ ≈ 2.5 coincides temporally with the appearance of SADs. Notably, we identify a nonthermal HXR source spatially associated with a well-defined SAD interacting with a supra-arcade spike. This spatiotemporal correlation—reported for the first time during the late decay phase—substantiates the association between SADs and ongoing magnetic reconnection. With the kink wave phase speed (≈400 km s −1 ) derived from spike oscillations and the density and temperature derived from a differential emission measure analysis, we estimate that the local magnetic field strength is in the range of 1.9–3.4 G, and the plasma β in the spike is on the order of unity. This analysis provides new insights into the physical nature of the supra-arcade structures and highlights the role of the magnetic field in their generation and evolution.