Filament activation and magnetic reconnection

A curved filament in a decaying active region (AR 8329) was observed on 9 September 1998 with a combination of several instruments, The main data base is a 4-hour long time series of 1 min cadence using the Lockheed tunable filter mounted in the Swedish Vacuum Solar Tower in La Palma (SVST). Filtergrams obtained at several wavelength positions in Halpha images are used to derive Doppler images. Interleaved images in the magnetic sensitive Fe I 6302.5 Angstrom line yield corresponding magnetograms. Supplementing observations are collected from TRACE and the French Multi-Channel Double Pass spectrograph (MSDP) mounted in the German VTT in Tenerife. The filament, which consists of several discrete fragments with nearly horizontal fine structures, under, goes activity and counter-streaming bulk flow, but without erupting. The magnetic field inversion line of this active region is complex and strongly influenced by intrusion of a positive polarity area in a following negative polarity of the region. The positive polarity area contains a small sunspot Surrounded by moving magnetic features (MMFs). The MMFs interact directly with the parasitic polarities in the filament channel, and thereby gives rise to merging and canceling magnetic flux. When the interaction occurs at the location of the feet ('barbs') of the filament notable activations are observed (ejection of 'blobs'). The ejections of 'blobs' are preceded by twist of filament threads and the 'blobs' move along downward bending field lines towards die photosphere close to the sound speed.