Abstract

We present 3D MHD simulations of the evolution of the coronal magnetic field as a line-tied twisted magnetic flux rope emerges quasi-statically into a pre-existing coronal potential arcade field. Through a sequence of simulations in which we vary the amount of twist transported into the corona be... Show moreWe present 3D MHD simulations of the evolution of the coronal magnetic field as a line-tied twisted magnetic flux rope emerges quasi-statically into a pre-existing coronal potential arcade field. Through a sequence of simulations in which we vary the amount of twist transported into the corona before the emergence is stopped, we investigate the conditions that lead to a dynamic eruption of the flux rope. It is found that the critical condition for the onset of eruption is for the center of the flux rope to reach a critical height at which the external potential field declines with height at a sufficiently steep rate, consistent with the onset of the torus instability of the flux rope. In some eruptive cases, immediately after the emergence is stopped, the coronal flux rope first settles into a quasi-static rise with an underlying sigmoid-shaped current sheeting developing. Reconnections in the current sheet allow the coronal flux rope to continue to rise quasi-statically to the critical height and dynamic eruption of the flux rope then ensues. We discuss the observational signatures with regard to the evolution of the X-ray sigmoid, post-flare loops, and the erupting filament, that may be produced based on the evolution of the magnetic field. Show less