Density and potential fluctuations were measured in the core region of the JIPP-TIIU plasma using a heavy ion beam probe. By applying a new technique of wavenumber resolved bicoherence, the coupling of the drift waves with zonal flows was clearly observed. In addition, nonlinear energy flow from drift-wave turbulence to high-frequency zonal flows using Ritz's model equation was first observed in the core region of low-density tokamak plasmas, which means there is generation of GAM by drift waves. The nonlinear growth rate of high-frequency zonal flow was estimated to be in the order of 104 s-1 or higher. In additionally heated plasmas where low-frequency ion temperature gradient mode is dominant, the bicoherence pattern changes drastically.
All Science Journal Classification (ASJC) codes
- Nuclear and High Energy Physics
- Condensed Matter Physics