Magnetic fluctuations during fast magnetic reconnection with a finite guide field in TS-3 plasma merging experiment

Large amplitude magnetic fluctuations with ion cyclotron range frequency was observed inside the diffusion region during fast magnetic reconnection with a finite guide field in TS-3 plasma merging experiment. Magnetic fluctuation measurement was performed by three kinds of magnetic probe array: a radial array of pickup coils in the direction of current sheet length to measure magnetic fluctuations of reconnected field Bz, an axial array in the direction of current sheet width to measure reconnecting field B// fluctuations, and a 3-componets (B//, Bx, Bz) probe to measure the dispersion relation of the fluctuations. The guide field at the X-point Bx is comparable to B//. The magnetic field variation caused by the fluctuations is larger than 10\% of B//. Reconnection rate had a positive correlation with the amplitude of fluctuations. Our numerical calculation of dispersion relation yields that Kinetic Alfv\'en Wave (left-handed polarization) can propagate in the vicinity of the X-point. Fluctuation measurement of 3-magnetic components suggests that the observed fluctuations are left hand polarized wave. As a consequence, the observed magnetic fluctuations with characteristic of KAW have good correlation with the enhancement of reconnection rate in the presence of a guide field.