Triggering Mechanism for the Filament Eruption on 2005 September 13 in NOAA Active Region 10808

Abstract

On 2005 September 13 a filament eruption accompanied by a halo coronal mass ejection (CME) occurred in the most flare-productive active region, NOAA 10808, in solar cycle 23. Using multiwavelength observations before the filament eruption on September 13, we investigate the processes leading to the catastrophic eruption. We find that the filament slowly ascended at a speed of 0.1 km s^-1 over 2 days before the eruption. During slow ascension, many small flares were observed close to the footpoints of the filament, where new magnetic elements were emerging. On the basis of the observational facts, we discuss the triggering mechanism leading to the filament eruption. We suggest that the process toward the eruption is as follows. First, a series of small flares played a role in changing the topology of the loops overlying the filament. Second, the small flares gradually changed the equilibrium state of the filament and caused the filament to ascend slowly over 2 days. Finally, a C2.9 flare that occurred when the filament was close to the critical point for loss of equilibrium directly led to the catastrophic filament eruption right after it.