High-Resolution Observation of Blowout Jets Regulated by Sunspot Rotation

Abstract

Coronal jets are believed to be the miniature version of large-scale solar eruptions. In particular, the eruption of a minifilament inside the base arch is suggested to be the trigger and even driver of blowout jets. Here, we propose an alternative triggering mechanism, based on high-resolution H\(\alpha \) observations of a blowout jet associated with a minifilament and an M1.2-class flare. The minifilament remains largely stationary during the blowout jet, except that it is straddled by flare loops connecting two flare ribbons, indicating that the magnetic arcade embedding the minifilament has been torn into two parts, with the upper part escaping with the blowout jet. In the wake of the flare, the southern end of the minifilament fans out like neighboring fibrils, indicative of mass and field exchanges between the minifilament and the fibrils. The blowout jet is preceded by a standard jet. With H\(\alpha \) fibrils moving toward the single-strand spire in a sweeping fashion, the standard jet transitions to the blowout jet. A similar pattern of standard-to-blowout jet transition occurs in an earlier C-class flare before the minifilament forms. The spiraling morphology and sweeping direction of these fibrils are suggestive of their footpoints being dragged by the leading sunspot that undergoes clockwise rotation for over two days. Soon after the sunspot rotation reaches a peak angular speed as fast as 10 deg h⁻¹, the dormant active region becomes flare productive, and the minifilament forms through the interaction of moving magnetic features from the rotating sunspot with satellite spots/pores. Hence, we suggest that the sunspot rotation plays a key role in building up free energy for flares and jets and in triggering blowout jets by inducing sweeping motions of fibrils.