In a study published in The Astrophysical Journal Letters, a research group led by Dr. SHEN Yuandeng from Yunnan Observatories of the Chinese Academy of Sciences reported the round-trip slipping motions of a circular flare ribbon, which manifests the round-trip slipping magnetic reconnection in the fan quasi-separatrix layer of a fan-spine magnetic system.

Magnetic reconnection is an important astrophysical process that converts magnetic free energy to kinetic energy, thermal energy, and radiant energy of particles, and plays a key role in the formation of solar eruptions. Due to the low-altitude impact of particle beams accelerated through magnetic reconnection whose locations reflect the footprints of separatrices or quasiseparatrix layers, flare ribbons are formed.

A fan-spine magnetic system is composed of a coronal null point, a dome-like fan that portrays the closed separatrix surface, and inner and outer spine field lines that belong to different connectivity domains. Observationally, one can expect three flare ribbons in a fan-spine eruption, i.e., an inner brightening surrounded by a circular ribbon relevant to the inner spine and the dome-like fan structures, and a remote ribbon associated with the outer spine.

In this study, the researchers revealed the fan-spine magnetic structure and confirmed the relationships between the field lines and the observed flare ribbons. They used high spatiotemporal resolution data provided by the New Vacuum Solar Telescope and the Solar Dynamic Observatory and nonlinear force-free magnetic field code.

For the first time, they reported the fast round-trip slipping motions of the circular flare ribbon.

The round-trip slipping motions of the circular ribbon manifested the slipping magnetic reconnection process in the fan quasi-separatrix layer, namely, the reconnection site was first move to the north and then changed its moving direction to the south. The northward motion was caused by the squeezing of a mini-filament eruption below the fan structure. When the filament eruption weakened or stopped, the system would undergo a recovery process, which account for the southward movement of the reconnection site in the fan quasi-separatrix layer.

 Contact

SHEN Yuandeng, Yunnan Observatories, CAS
Email: ydshen@ynao.ac.cn