Study of non-linear coupling of fluctuations at long distance in LHD

摘要

Non-linear coupling between fluctuations at different radial locations is observed on the Large Helical Device (LHD) plasma. The summed bi-coherence between the low frequency macro-scale fluctuation (frequency is f = 2.75 kHz) at ρ = r_(eff)/a_(99) = 0.63 (where a_(99) is averaged plasma radius) and the high-frequency micro-scale fluctuations (frequency range of f ＞ 150 kHz) at ρ = 0.88 is found to converge to a non-zero and finite value. The bi-phase analysis provides another basis for the non-linear interaction across the long distance. These results are associated with the violation local closure for transport relation.