Stereoscopic diagnosing of a filament-cavity flux rope system by tracing the path of a two-sided-loop jet

The fine magnetic structure is vitally important to understanding the formation, stabilization and eruption of solar filaments, but so far, it still an open question yet be resolved. Using stereoscopic observations taken by Solar Dynamics Observatory TErrestrial RElations Obsevatory, we studied generation mechanism a two-sided-loop jet (TJ) ejection process plasma into overlying filament-cavity system. We find that was due reconnection between emerging flux loop filament. jet's two arms ejected along filament axis during initial stage. Then, north arm bifurcated parts at about 50 Mm from site. After bifurcation, were cavity which hosted filament, respectively. By tracing ejecting flows TJ inside not only measured twist stored in least 5$\pi$ also found rope system well agreement with theoretical results Magnetic models.