Yue Fang

Failed filament eruptions have been reported previously; however, the responsible physical mechanisms remain debated. Using multiwavelength data from Solar Orbiter and Solar Dynamics Observatory, we analyze a failed filament eruption on 2024 March 19. The filament initially manifested as an extreme-ultraviolet (EUV) filament channel and rose without any enhancement in hard X-ray emission. As it subsequently transitioned from acceleration to deceleration, its main axis developed a Y-shaped kink structure, and the hard X-ray flux peaked during the deceleration phase. Brightenings were detected, spatially corresponding to the opposite polarities where the loops overlying the filament channel were rooted. Reconstructed hard X-ray sources revealed the existence of a coronal source at the leading edge of the erupting structure. After the eruption, the overlying loops were heated, and bright materials were observed moving along them. A data-constrained magnetohydrodynamic simulation further demonstrated that the eruptive flux rope interacted with its overlying loops, with its footpoint drifting into the region where the overlying loops were rooted, strongly confirming that external reconnection with the overlying loops eroded the eruptive flux. We also analyzed the decay index above the flux rope before the eruption and found that the flux rope was in the torus stable domain. We propose a possible scenario in which the eruption is initially driven by kink instability, after which external reconnection with the overlying loops leads to its deceleration and ultimately to the failure of the eruption.

Although interactions between filaments and other atmospheric structures are frequently observed, detailed studies on how these interactions affect the dynamics of the involved structures remain scarce. Here we present an analysis of a filament eruption on 2023 December 31, during which the filament interacted with a nearby coronal loop (L1). Throughout the interaction, the filament continued erupting. At the interaction site, the bright emission appeared within L1 while the filament exhibited a local deceleration here, regaining its velocity only after the bright emission disappeared. Multiwavelength observations and differential emission measure analysis indicated that the bright emission resulted from a marked increase in plasma density rather than in temperature. We propose that the plasma accumulation in L1 was a consequence of condensation induced by the interaction with the filament. The condensation influenced the velocity of the erupting filament in turn. As the condensation drained away, the filament recovered its velocity. Our observations suggest that condensation induced by the interaction can exert dynamic feedback on the erupting filaments.

Here we study a filament eruption on 2023 April 21. The filament was composed of two segments, named S1 and S2. Initially, the brightening and bidirectionally plasmoid flows appeared inside S1, and then the west part of S1 (WS1) experienced rapid rising and eruption, accompanied by coronal dimming, flare ribbons, and a secondary flare ribbon. However, the east part of S1 (ES1) rose slowly and was confined. The material within ES1 drained back to its eastern footpoint, resulting in the footpoint brightening. In the later phase, the south footpoint of the stable extreme-ultraviolet (EUV) loops overlying ES1 was brightened also, which may result from the disturbance of drainage. During S1 eruption and activation, S2 remained stable. Nonlinear force-free field extrapolation shows that the footpoints of the magnetic field lines overlying WS1 are rooted on the flare ribbons, while the field lines overlying ES1, which share a negative field with other lines, correspond to the stable EUV loops. Based on potential field extrapolation, we calculate the decay index of the background fields overlying the filament. It indicates that the critical height of the torus instability of the fields overlying WS1 is lower than that overlying ES1. To interpret this filament eruption, we first put forward the eruptive duality, characterized by the eruption of the partial filament structure and the confinement of the other structure, and this duality is determined by the properties of the overlying fields.

Although the magnetic field structures of solar filaments have been studied for several decades, the detailed evolution of the structure around a filament prior to its eruption is rarely observed. On 2021 October 28 in AR 12887, a major solar flare (X1.0 class) occurred at 15:35 UT. Based on the Solar Dynamics Observatory high-spatial-resolution observations, we find this flare is associated with the eruption of two filaments, namely F1 and F2. The two filaments are initially independent. The western leg (WLEG) of F1 approaches the northern leg of F2, due to the continuous movement and rotation of the magnetic field in which the WLEG roots in. We find first that there are some threads wrapping the WLEG. Brightening and bidirectionally plasmoid flows that originate from a brightening are detected in these threads, then the threads disappear, and the two filaments connect. NLFFF extrapolation reveals that there is a toroidal magnetic structure enveloping the WLEG and corresponding spatially to the threads. It is expected that a filament is enveloped by toroidal magnetic fields. According to the observations and extrapolation, we suggest that these threads represent the toroidal magnetic fields wrapping the WLEG. This paper provides new details about the dynamics of the toroidal magnetic fields. Magnetic reconnection takes place in the toroidal fields and thus destroys the fields, then F1 and F2 connect, and subsequently, the two filaments erupt and the flare occurs.