Modelling the magnetic structure of a large-scale horse-shoe-like filament in a decaying and diffuse active region

ABSTRACT A large-scale, horse-shoe-like filament was investigated and the magnetic field around it reconstructed. This is an intermediate (IF) that appeared on solar disc for first time at 02:00 ut 2015 November 7, took 8 d to move central median disc. The active region AR 12452 which occurred diffuse so nearby weak, average strength 106 G. Therefore, existing approaches extrapolating coronal constructing configuration in with strong background do not work well here. On basis of regularized Biot–Savart laws method, we successfully constructed a data-constrained, non-linear force-free this IF observed 14. overall obtained way matches morphology suggested by 304 Å image taken Atmospheric Imaging Assembly board Solar Dynamics Observatory. Magnetic dips were coincident space H α features filament, lower altitude than seen Å. suggests cold plasma fills part hot situated higher region. quasi-separatrix layer wraps both electric current are stronger near inner edge filament.