Figure 1. Comparison of the observed and the reconstructed filaments. The left panel indicates the filaments observed from STEREO A. The right panel indicates the reconstructed filaments seen from STEREO A view. The colors in the right panel denote the height from the solar disk.

Using the data from spacebased instrument (STEREO), Ting Li et al. investigate three-dimensional (3D) shape and evolution of two eruptive filaments. They first obtain the true dynamic evolution of different locations along the axis of the large filament (LF). This study will be published recently in The Astrophysical Journal (Ting Li, Jun Zhang, Hui Zhao, & Shuhong Yang).

Solar filaments are relatively cool and dense plasma suspended in the hot and tenuous corona. Filament eruptions are one of the most spectacular active phenomena, and they are often associated with flares and coronal mass ejections (CMEs). Thus, a detailed study of the triggering mechanism of filament eruptions and their relationships with flares and CMEs is very important, which will lead to a good ability to forecast CMEs and associated space weather.

Former studies are based on the single-viewpoint observations, which are influenced by projection effect. After the launch of STEREO satellite, two-viewpoint observations could be used to investigate the 3D shape of filament eruptions. Using observations from STEREO, Li et al. reconstruct two eruptive filaments and study the true eruption process of the reconstructed filaments. This event is the most spectacular eruptive filaments in the recent three years. For the first time, they investigate the true velocities and accelerations of different locations along the axis of the LF, and find that the velocity and acceleration vary with the measured location and the highest points are not always fastest. The filament eruptions are associated with a slow CME , and this event is one example of a gradual filament eruption associated with a gradual CME. In addition, the moving direction of the LF changes from a non-radial in the low corona to a nearly radial direction in the outer corona.