Photospheric magnetic field changes associated with the activations of a quiescent filament

The disturbances of a quiescent filament and associated evolution of photospheric magnetic field were examined. The whole filament was broken into three sections by two filament breaks. In different sections, three distinct disturbances took place: two major ones with similar characteristics and a transient one. The presence of filament twist and the highly sheared filament magnetic field were clearly revealed by the velocity patterns during the two major disturbances. In photospheric magnetograms, both filament breaks located between opposite polarity magnetic elements with obvious changes of magnetic flux. The two opposite polarity knots at one break showed increasing flux but no interaction. At the other break, however, the two opposite polarity elements not only increased in flux but also collided with each other, and so led to a relatively steep field gradient across the axis of the filament; it was evident that flux cancellation and resultant reduction of field gradient occurred here. In addition, several ephemeral regions and small cancelling magnetic features (CMFs) appeared in the filament channel in the course of filament disturbances. The cause of the filament disturbances was interpreted as slow magnetic reconnection resulting from the flux emergence and cancellation, and the possible formation process of filament twist is discussed.