Authors: Jeongwoo Lee (NJIT)

We studied the 2014 January 1 flare accompanied by a CME from NOAA active region 11936. The images from the Atmospheric Imaging Assembly (AIA) on board SDO together with a nonlinear force-free field (NLFFF) extrapolation from SDO/HMI magnetograms show two filament flux ropes (FR1 and FR2) pre-existing before the flare. They extend over 30,000 km altogether with their portions intertwined with each other. When a partial eruption begins from FR1 creating a circular ribbon and remote brightenings around it, the disrupted FR2 initially moves together with FR1 but falls back to drain towards its eastern ends and ends up with a failed eruption. Since the intertwined portion is subject to the same decay index, the torus instability, which drives the eruption of magnetic flux rope due to the rapid decay of the ambient magnetic field, cannot fully explain the decoupling of FR1 from FR2.  For an additional factor making one a successful eruption and the other a failed eruption in this double-flux-rope system, we suggest that magnetic reconnection over a sheared magnetic arcade added more twisted fluxes to FR1 to make it successfully erupt, while FR2 remains tied down to the photosphere.