高能暂现源 · 每日文献综述

Photometric space missions like Kepler and TESS have revealed unprecedented statistics of stellar flares, including the frequent detection of highly energetic superflares. Spectroscopic characterization of flares and especially superflares, however, is still not as commonly available. In contrast to broad-band photometry, spectroscopic data can give more insights into the physical parameters of flares, as well as allowing to identify possibly accompanying CMEs. In this context, we monitored the young planet-hosting flare star AU Mic for about 60 partial nights (>160 hours) between 2022 and 2023 spectroscopically with the ESO 1.52m telescope hosted by the PLATOSpec consortium. Here, we report on the search for signatures of flares and CMEs in these data, including the partial observation of a possible extreme superflare.

We investigate the successful eruption of a C-shaped filament within a two-filament system on 2014 March 29. Its northern leg overlaps with an adjacent inverse-L-shaped filament to the west. Preeruption observations from the Atmospheric Imaging Assembly and Helioseismic and Magnetic Imager onboard the Solar Dynamics Observatory reveal persistent activation near the western filament and 1 hr of magnetic flux cancellation beneath the middle segment of the erupting filament. To understand the initiation and evolution of the filament eruption, we conduct magnetic field modeling and further compare this event with a confined filament eruption in a double-decker filament system that occurred in a similar photospheric magnetic configuration on 2014 July 5. In the confined event, the eruptive filament is supported by a flux rope beneath a dome-shaped quasi-separatrix layer (QSL). The flux rope erupts due to torus instability and subsequently reconnects with the overlying fan fields, resulting in flux-rope erosion and ultimately a failed eruption. In comparison, the successful filament is situated beneath a hyperbolic flux tube (HFT) sandwiched between two arch-shaped QSLs. Flare reconnection triggered by flux cancellation at the filament's middle section initiates the eruption. Dominant breakout reconnection occurring at the overlying HFT reduces part of the magnetic confinement, thereby facilitating the successful eruption. Additionally, the substantially lower flux ratio of outer to inner polarities (1.0, compared with 5.3 in the confined event) also contributes to the success of the filament eruption.