Solar filaments are accumulations of cool, dense, partially ionized plasma that are suspended in the solar corona against gravity. They lie above polarity inversion lines in the photospheric radial magnetic field. When they are viewed on the solar disk, they show strong absorption in Hα and in the Extreme Ultraviolet (EUV) continuum, and are called “filaments.” When they are seen above the solar limb, they are bright features against a dark background, and are called "prominences.”

Often, the terms “filament” and “prominence” are used interchangeably. Prominence plasma is embedded in special magnetic structures and thermally isolated from the surrounding environment. Usually, solar filament eruptions are associated with solar flares and coronal mass ejections (CMEs). The study on solar filament eruptions is a very important subject in solar physics.

To address the detailed process of solar filament eruptions, Dr. YAN Xiaoli and collaborators studied a failed solar active-region filament eruption associated with a C-class flare by using high-resolution H-alpha images from the New Vacuum Solar Telescope (NVST), supplemented by EUV observations of the Solar Dynamical Observatory (SDO). Their research was published on The Astrophysical Journal.

They found a small bi-pole magnetic field emerged below the filament before the filament eruption. And then magnetic reconnection between the filament and the emerging bi-pole magnetic field triggered the filament eruption. During the filament eruption, the untwisting motion of the filament can be clearly traced by the eruptive threads.

Moreover, the foot-points of the eruptive threads are determined by tracing the descending filament materials. Note that the filament twisted structure and the right part of the eruptive filament threads cannot be seen before the filament eruption. These eruptive threads at the right part of the filament are found to be rooting in the weak negative polarities near the main negative sunspot. Moreover, a new filament formed in the filament channel due to material injection from the eruptive filament.

The above observations and the potential field extrapolations are inclined to support that the filament materials were transferred into the overlying magnetic loops and the nearby filament channel by magnetic reconnection. The observation is different from the scenario in the standard model of solar filament eruption. Therefore, this study sheds light on better understanding on the complexity of filament eruptions.

Contact:

YAN Xiaoli, YNAO, CAS

yanxl@ynao.ac.cn