Sunspot Rotation Leading to Coronal Mass Ejection

Abstract The rotation of sunspots around their umbral center has long been considered as an important process in driving coronal mass ejections (CMEs), but the specific mechanism remains unclear. Here with numerical magnetohydrodynamic simulations of both data-inspired and data-driven approaches, we show that the rotation of a large sunspot leads to a CME actually in a way distinct from the conventional view based on ideal instabilities of twisted flux rope. It is found that through the successive rotation of the sunspot the coronal magnetic field is sheared with a vertical current sheet created progressively, and once fast reconnection sets in the current sheet, the eruption is instantly triggered, with a highly twisted flux rope originating from the eruption. The simulations also revealed a slow-rise evolution phase sandwiched between the quasi-static energy-storage phase and the impulsive eruption-acceleration phase, and it enhances building up of the current sheet.