A Fan Spine Jet: Nonradial Filament Eruption and the Plasmoid Formation

Using the data from SDO and NVST, we studied a circular filament eruption in association with the formation of jet under a nonaxisymmetric fan spine configuration. A nonradial motion of the filament toward a null point and the formation of a jet were presented in detail. This event contained a small circular filament, which was located above the polarity inversion line. The nonlinear force-free field extrapolation shows the presence of a nonaxisymmetric fan spine structure above the filament. Thus, the filament was confined by this magnetic field structure. Since the confining magnetic pressure decreases much faster toward the null point than anywhere else, the filament displayed a shift motion toward the null point that resulted in a collision, and a reconnection signature of bidirectional flows was observed. Due to the external magnetic reconnection, the topology of the filament field was reconfigured, accompanying by the scattered filament material spreading along nearby coronal loops, which resulted in a blowout jet. Particularly, some ejected plasma blobs were also observed in the vicinity of the interfaces between the filament and neighboring coronal loops. These blobs originating from the dissipation region may be plasmoids in association with tearing mode instability. We suggested that in pre jet phase the nonaxisymmetric fan spine configuration can act on the erupting filament, laterally deflecting and channeling its motion toward the null point, which may facilitate the jet formation by magnetic reconnection.