Plasma motions in a short-lived filament related to a magnetic flux cancellation

¹ Dipartimento di Fisica e Astronomia - Sezione Astrofisica, Università di Catania, via S. Sofia 78, 95123 Catania, Italy e-mail: fzu@oact.inaf.it
² INAF - Osservatorio Astrofisico di Catania, via S. Sofia 78, 95123 Catania, Italy

Received: 12 October 2006
Accepted: 2 February 2007

Abstract

Context.In recent years the mechanisms responsible for filament formation and evolution have been investigated by many authors. In particular, the role played by the processes of magnetic flux cancellation in building up or destroying filaments is still a matter of debate.

Aims. In this paper we analyze the evolution of an active region filament that formed in NOAA 10 407 on 14 July 2003, to investigate the phenomena responsible for its destabilization and short lifetime (~12 h).

Methods.This analysis is based on high-resolution H_α data acquired by THEMIS operating in IPM mode, on H_α data acquired at Big Bear Solar Observatory, and on MDI/SOHO magnetograms. Using these data, we determined the morphological, dynamical, and magnetic evolution of the filament.

Results.The chromospheric images show two dark surges occurring sequentially in the northern part of the filament, besides two bright H_α patches located in the same area; from analysis of the photospheric magnetograms, we could infer that a magnetic flux cancellation had occurred in this area.

Conclusions.The presence of a cancelling magnetic feature (CMF) in the same area where the dark H_α surges occurred, the temporal behavior of the velocity fields in the surges, and the presence of bright H_α patches in the CMF area, suggest a scenario where the coronal arcade initially sustaining the filament might have undergone consecutive reconnection processes. From the concurrence of these events with the filament activation and successive disappearance, we believe that the arcade field lines, after the reconnection events, changed such that the plasma filament was no longer confined in the arcade: this led to its destabilization and disappearance.