| Abstract: | We report in this paper the analysis of the evolution of a magnetic fragment observed in NOAA 9445 on 5 May, 2001. This magnetic fragment emerged laterally to a filament which later split into two parts. The bifurcation site coincided with the magnetic fragment location and the part of the filament which split was later destabilized and a flare occurred. The magnetic flux variations in the magnetic fragment and in the surrounding area were analyzed and, considering their trends and other observational signatures (Hα brightenings and associated plasma motions), we could infer that it was a cancelling magnetic feature (CMF).We determined some geometrical and physical parameters of the CMF (area, magnetic flux variation, cancellation speed and flux cancellation rate) using high resolution magnetograms taken by BBSO. We compared the observed parameters of the CMF with the parameters of low‐lying reconnection current sheets given in the model proposed by Litvinenko (1999) and found good agreement between observed and theoretical values. Therefore, we conclude that a low‐lying magnetic reconnection process might be the cause of the filament activation. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) |
