Current-density fluctuations and ambipolarity of transport

The fluctuation in the plasma current density is measured in the MST reversed-field-pinch experiment. Such fluctuations, ad the measured radial profile of the k spectrum of magnetic fluctuations, support the view that low-frequency fluctuations (f<30 kHz) are tearing modes and high-frequency fluctuations (30 kHz<f<250 kHz) are localized turbulence in resonance with the local equilibrium magnetic field (i.e., k⋅B=0). Correlation of current-density and magnetic fluctuations (〈j${\mathrm{̃}}_{\mathrm{\parallel }}$B${\mathrm{̃}}_{\mathit{r}}$〉) demonstrates that radial particle transport from particle motion parallel to a fluctuating magnetic field is ambipolar over the full frequency range.