Three-minute Sunspot Oscillations Driven by Magnetic Reconnection in a Light Bridge

Abstract

We report a different type of three-minute chromospheric oscillation above a sunspot in association with a small-scale impulsive event in a light bridge (LB). During our observations, we found a transient brightening in the LB. The brightening was composed of elementary bursts that may be a manifestation of fast repetitive magnetic reconnections in the LB. Interestingly, the oscillations in the nearby sunspot umbra were impulsively excited when the intensity of the brightening reached its peak. The initial period of the oscillations was about 2.3 minutes and then gradually increased to 3.0 minutes with time. In addition, we found that the amplitude of the excited oscillations was twice the amplitude of oscillations before the brightening. Based on our results, we propose that magnetic reconnection occurring in an LB can excite oscillations in the nearby sunspot umbra.