Presentation Open Access
Karna, Nishu; Savcheva, Antonia
In this study, the magnetic configuration of a coronal sigmoid is presented. The sigmoid was observed by Hinode/XRT and SDO/AIA in the NOAA active region 12665 between July 6th-18th, 2017. We construct a Non-Linear Force-Free Field (NLFFF) model of a sigmoid observed on July 13th 2017 at 18:22 UTC using the flux-rope insertion (FR) method and relaxed the magnetic field toward a force-free state using magnetofrictional relaxation (MF). The NLFFF model produces the 3D coronal magnetic field constrained by observed coronal structures and photospheric magnetograms. SDO/HMI magnetograms were used as input of the models. The resulting magnetic field configurations were compared with Hinode/XRT and SDO/AIA images of the same region to determine the best-fit model. The sigmoid is modeled in both stable and unstable states to represent various stages of evolution in the sigmoid; the best-fit stable model has a poloidal flux of -3E10 Mx and axial flux of 2E21 Mx, whereas the best-fit unstable model has a poloidal flux of -1E10 and an axial flux of 5e21. Additionally, similar models were produced for a time earlier in the development of the active region on July 12th, 2017 at 03:17 UTC where a small jet is observed in the elbow of the sigmoid. The goal of our study is to reproduce the pre-flare configuration so that we can understand the eruption and have a NLFFF model for the magnetic environment in which the jet is erupting.