Cross-sectional view of the TS-3 device (a), typical magnetic structure around the reconnection region together with the locations of high-frequency fluctuation pickup coils (red circles—δB r , green circles—δB z ) (b), typical axial profile of radial (reconnecting) magnetic field B r (c), and radial profile of axial (reconnected) field B z (d) across the X-point.
Temporal evolution of the 2-D magnetic structure near the X-point. Poloidal magnetic flux surfaces are marked as solid black lines with contour spacing of 0.3 mWb; toroidal current density is shown in color.
Time evolutions of the fluctuation signal δBr measured at two different toroidal angles (a), and their Fourier spectra (b).
Evolution of the radial profile of the magnetic fluctuation δB z measured at the center of the current sheet for three different discharges. Red and blue colors indicate positive and negative fluctuation signals. Red solid curve indicates the radial position of the X-point; black broken curves indicate the upper and lower edges of the current sheet.
Schematic of the propagation of the magnetic fluctuation during magnetic reconnection with a guide field.
Perpendicular wavenumbers (a), and phase velocities (b) as functions of guide field calculated from the dispersion relation for low-frequency waves.
Evolution of the magnetic fluctuation signal δBz (a) and the reconnection electric field (dashed line: temporal evolution, solid line: moving average) (b). Correlation between the normalized fluctuation amplitude δB z /B r and maximal reconnection electric field (c).
Radial profiles of the reconnected magnetic field (a) and (c) and schematics of the magnetic field structure near the X-point (b) and (d). (a) and (b) for the timing before fluctuation onset, and (c) and (d) for that during fluctuation. (e) shows the axial profiles of reconnecting magnetic field fluctuation across the current sheet.
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