The Magnetic Flux Rope Structure of a Triangulated Solar Filament

Solar magnetic flux ropes are core structures driving solar activities. We construct a magnetic flux rope for a filament/prominence observed at 01:11 UT on 2011 June 21 in AR 11236 with a combination of state-of-the-art methods, including triangulation from multiperspective observations, the flux rope embedding method, the regularized Biot-Savart laws, and the magnetofrictional method. First, the path of the filament is reconstructed via the triangulation with 304 Å images observed by the Atmospheric Imaging Assembly on board Solar Dynamics Observatory (SDO) and by the Extreme Ultraviolet Imager on board the twin Solar Terrestrial Relations Observatory. Then, a flux rope is constructed with the regularized Biot-Savart laws using the information of its axis. Next, it is embedded into a potential magnetic field computed from the photospheric radial magnetic field observed by the Helioseismic and Magnetic Imager on board SDO. The combined magnetic field is finally relaxed by the magnetofrictional method to reach a nonlinear force-free state. It is found that both models constructed by the regularized Biot-Savart laws and after the magnetofrictional relaxation coincide with the 304 Å images. The distribution of magnetic dips coincides with part of the filament/prominence material, and the quasi-separatrix layers wrap the magnetic flux ropes, displaying hyperbolic flux tube structures. These models have the advantages of constructing magnetic flux ropes in the higher atmosphere and weak magnetic field regions, which could be used as initial conditions for magnetohydrodynamic simulations of coronal mass ejections.