Recurring homologous solar eruptions in NOAA AR 11429

Abstract

We present the study of three homologous solar eruptions from NOAA active region (AR) 11429 over four days. This large and complex AR is divided into two relatively simple subregions: northeast (NE) and southwest (SW). Recurrent eruptions occurred from the SW subregion over different evolutionary phases, which provided a unique opportunity to isolate the physical processes responsible for solar eruptions. Persistent shearing and convergence of opposite magnetic polarities led to continuous flux cancellation along the SW polarity inversion line (PIL). A filament persistently lying along the SW PIL was observed to survive each eruption, which suggests a partial eruption of the magnetic system. Further, following the first and second eruptions, a sigmoidal magnetic structure of similar morphology was reformed along the SW PIL. The photospheric motion of magnetic flux continuously injected and stored the negative helicity in the partially erupted magnetic system and built up the magnetic free energy for the successive eruptions. These results suggest that the shearing motion and magnetic flux cancellation of opposite fluxes were: (1) the dominant factor, irrespective of the evolutionary phase, that contributed to the recurrent homologous eruption, and (2) the key processes of forming the erupting structure, likely a magnetic flux rope; its long-lasting continuation results in the reformation of an identical erupting structure. The study also finds that similar magnetic topology could result in the magnetic reconnection at the same location, and such flares during the precursor phase would help in the eruption by decreasing the constraint of the overlying magnetic field.