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Nagashima, Yoshihiko*; Ito, Kimitaka*; Ito, Sanae*; Fujisawa, Akihide*; Hoshino, Katsumichi; Takase, Yuichi*; Yagi, Masatoshi*; Ejiri, Akira*; Ida, Katsumi*; Shinohara, Koji; et al.
Plasma Physics and Controlled Fusion, 48(4), p.S1 - S15, 2006/04
Times Cited Count：36 Percentile：74.41(Physics, Fluids & Plasmas)This paper presents the results of bispectral analysis of floating potential fluctuations in the edge region of ohmically heated plasmas in the JFT-2M tokamak. Inside of the outermost magnetic surface,coherent modes were observed around the frequency of geodesic acoustic mode which is a kind of the zonal flow. The squared bicoherence shows significant nonlinear couplings between the coherent fluctuations and the background fluctuations (which are likely to contain drift wave turbulent fluctuations). The experimental results that the total bicoherence is proportional to the squared amplitude of the coherent fluctuation, and that the biphase of the coherent modes localizes around a constant value 
, are consistent with the theoretical prediction on the drift wave - zonal flow systems based on the Hasegawa-Mima model.
Li, J.; Kishimoto, Yasuaki
Physics of Plasmas, 9(4), p.1241 - 1254, 2002/04
Times Cited Count：37 Percentile：72.43(Physics, Fluids & Plasmas)Zonal flows can be generated by drift wave turbulence through the nonlinear interactions. 3-D gyrofluid simulations show that in a turbulent system driven by electrostatic sheared slab electron temperature gradient(ETG) modes, the excitation of zonal flows is a slower process that indicates the amplitudes grow up approximately proportionally to time. The zonal flows are very weak comparing with the background turbulence and hardly work for suppressing the turbulent electron heat transport. The dynamics of zonal flows is numerically explored through starting zonal flow component in the quasi-steady state.
