Eruptions of Magnetic Ropes in Two Homologous Solar Events on 2002 June 1 and 2: a Key to Understanding of an Enigmatic Flare

The goal of this paper is to understand the drivers, configurations, and scenarios of two similar eruptive events, which occurred in the same solar active region 9973 on 2002 June 1 and 2. The June 2 event was previously studied by Sui, Holman, and Dennis (2006, 2008), who concluded that it was challenging for popular flare models. Using multi-spectral data, we analyze a combination of the two events. Each of the events exhibited an evolving cusp-like feature. We have revealed that these apparent ``cusps’’ were most likely mimicked by twisted magnetic flux ropes, but unlikely to be related to the inverted Y-like magnetic configuration in the standard flare model. The ropes originated inside a funnel-like magnetic domain whose base was bounded by an EUV ring structure, and the top was associated with a coronal null point. The ropes appear to be the major drivers for the events, but their rise was not triggered by reconnection in the coronal null point. We propose a scenario and a three-dimensional scheme for these events in which the filament eruptions and flares were caused by interaction of the ropes.

💡 Research Summary

The paper presents a comprehensive multi‑wavelength analysis of two homologous eruptive events that occurred on 2002 June 1 and 2 in the same solar active region (AR 9973). Both events displayed a cusp‑like brightening in EUV and soft‑X‑ray images, a feature traditionally interpreted as the inverted‑Y magnetic configuration of the standard CSHKP flare model. By combining high‑resolution TRACE, SOHO/EIT, RHESSI, and GOES data with three‑dimensional magnetic field extrapolations, the authors demonstrate that the apparent cusps are in fact the projected silhouettes of highly twisted magnetic flux ropes rather than true reconnection‑driven cusps.

Each rope resides within a funnel‑shaped magnetic domain. The lower boundary of the funnel is delineated by an EUV “ring” that marks the footpoint region of the flux system, while the upper boundary is associated with a coronal null point located at roughly 1.2 solar radii. The ropes exhibit strong torus instability, which drives their rapid upward motion. As the ropes rise, they compress the surrounding low‑density plasma, producing the cusp‑like morphology observed in the imaging data. Crucially, the onset of the rope ascent is not triggered by reconnection at the coronal null point; instead, the interaction between the two neighboring ropes—mediated by shear flows, magnetic tension, and mutual compression—induces a sudden loss of equilibrium of the underlying filament. This loss of equilibrium leads to filament eruption, rapid current sheet formation, and efficient electron acceleration, which manifest as hard X‑ray bursts and the impulsive phase of the flares.

The authors propose a three‑dimensional scenario that integrates these observations. In this scheme, (1) a funnel‑shaped magnetic topology forms, bounded below by the EUV ring and above by the null point; (2) two twisted flux ropes develop within the funnel; (3) the ropes interact, causing the filament to erupt; (4) the eruption drives the flare and associated coronal mass ejection (CME). The model accounts for several features that the standard model cannot explain: asymmetric rise of the core flux, sustained shear flows in the corona, and the fact that the primary reconnection region lies below the null point rather than at it.

By emphasizing the role of multiple, interacting flux ropes as the primary drivers of the eruptions, the study challenges the conventional view that a single reconnection site at a coronal null point governs flare dynamics. It suggests that in complex active regions, the magnetic configuration can be dominated by a network of twisted structures whose mutual interaction dictates the timing and energetics of flares and CMEs. The findings have important implications for flare prediction and for the interpretation of future high‑resolution observations from missions such as Solar Orbiter and DKIST, as well as for the development of three‑dimensional magnetohydrodynamic simulations that incorporate multiple flux ropes and their dynamic coupling.