Authors: Arpita Roddanavar (NJIT), Satoshi Inoue (NJIT), Keiji Hayashi (NJIT), Ju Jing (NJIT), Wenda Cao (NJIT), Haimin Wang (NJIT)

Solar active region 11283 produced an X2.1 flare associated with a solar eruption on September 6, 2011. Observations revealed a pre-flare sigmoidal structure and a circular flare ribbon surrounding the typical two-ribbon structure, along with remote brightenings at a considerable distance from the main flare site. To interpret these observations in terms of the three-dimensional (3D) coronal magnetic field dynamics, we conducted data-constrained magnetohydrodynamic (MHD) simulations. Using a non-linear force-free field (NLFFF) as the initial condition, we reconstructed a realistic pre-flare magnetic environment, capturing a sheared sigmoid above the polarity inversion line (PIL) and a fan-spine structure. Our simulations revealed that reconnection between the sigmoidal field and neighboring large-scale, nearly potential field nearby the region with strong current density facilitated the transfer of magnetic twist, leading to the formation of a large magnetic flux rope (MFR). This twist propagation was observed throughout the MFR length. Additionally, we found that the transfer of twist to the fan-spine structure allowed it to expand along the main flux rope. The footpoints of the newly formed MFR were significantly separated, with one footpoint aligned with the circular flare ribbon and the other anchored at the remote brightening region. Our findings suggest that a large MFR formed during the X2.1 flare, providing a coherent explanation for the observed phenomena.