Data-constrained MHD simulation for the eruption of a filament-sigmoid system in solar active region 11520

We construct a data-constrained magnetohydrodynamic simulation of the filament–sigmoid system with the flux rope insertion method and magnetic flux eruption code, which produces a magnetic field evolution that may explain the separation of the low-lying filament and high-lying hot channel (sigmoid).

The initial state of the magnetic model contains a magnetic flux rope with a hyperbolic flux tube, a null-point structure, and overlying confining magnetic fields. We find that the magnetic reconnections at the null point make the right footpoint of the sigmoid move from one positive magnetic polarity (P1) to another (P3). The tether-cutting reconnection at the hyperbolic flux tube occurs and quickly cuts off the connection of the low-lying filament and high-lying sigmoid.