The Sun Filament Activation And The Outbreak Of Observational Studies

The study of solar filament activations and eruptions is important not only in understanding formation, supporting and stability of filaments in general, but also in understanding violent solar eruptions such as flares and coronal mass ejections. In the present paper, the observational and theoretical progresses in the more recent study of structure, dynamics and magnetic field configuration of filament are introduced; the observational characteristics, disturbing agents, possible driving mechanisms and theoretical models of filament instability are also summarized. It is studied for the detailed morphological and dynamic evolution of several disturbed filaments, the relevant changes of photospheric magnetic field and coronal structure, as well as the development of associated flares. The main results are included as follows: 1 .Once filaments are disturbed, the presence of twisted structure and motion is not an uncommon result, and the filament twist need not to be great enough to lead to an eruption. The fact suggests that twisted magnetic field may commonly exist in disturbed filament. For the first time, we found a unique 搗elocity rope?pattern during the activating process of a quiescent filament, which clearly revealed the twisted field in the disturbed filament. 2.Jn study of the filament disturbances in an active region, we showed that the filament underwent successive activation and each disturbance was followed by a flare, but it did not erupt or disappear. For the first time, we fount that the activation of the whole filament could be resulted from the disturbance of one of twisted filament threads, while the other threads remain nearly stationary. 3.For the first time, we identify that the helical structure appeared in an eruptive sinistral filament was left-helical one. Such identification is consistent with Martin & McAllister抯 predication (1997) but at odds with Rust & Kumar抯 (1994) assumption; we further refer that magnetic field of filaments is not helical in their quiescent status and helical structure during filament disturbance is formed by magnetic reconnection between non-helical structures. 4.The filament disturbances are closely associated with photospheric displacement and changes of photospheric magnetic field in filament channel. The pore birth and movement, the sunspots squeeze and shear, the magnetic flux emergence and cancellation may be all contributed to loss of filament stability. 5 .The cause of filament destabilization is interpreted as steady cancellation reconnection in the photosphere layer. Such pre-eruptive reconnection lead to the accumulation of magnetic flux and complexity in filament via inducing current and changing the magnetic tether of filament to the photosphere, so directly relevant to filament disturbances. In the study of the eruption of an active-region filament, which was obviously driven by an emerging bipole, we found that the eruption was due to the interaction between the bipole and the X-ray loops overlying the filament, and we provided clear evidence that slowly photospheric reconnection in their interface occurred during the bipole emergence.