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

TL;DR

This study investigates the gradual buildup and triggering process of a filament eruption in NOAA 10808 on September 13, 2005, highlighting the role of small flares and magnetic topology changes leading to a catastrophic eruption.

Contribution

It presents a detailed observational analysis of the pre-eruption processes, proposing a new mechanism involving small flares and magnetic topology changes as triggers.

Findings

Gradual filament ascent over two days before eruption

Small flares near filament footpoints alter magnetic topology

A C2.9 flare triggers the eruption at critical equilibrium

Abstract

On 2005 September 13 a filament eruption accompanied by a halo CME occurred in the most flare-productive active region NOAA 10808 in Solar Cycle 23. Using multi-wavelength observations before the filament eruption on Sep. 13th, we investigate the processes leading to the catastrophic eruption. We find that the filament slowly ascended at a speed of 0.1km/s over two days before the eruption. During slow ascending, 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 the process toward the eruption 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 two 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 itself.