Wave-number spectral scaling law of drift wave-zonal flow turbulence in gyrofluid simulations

Wave-number spectral characteristics of ion temperature gradient (ITG) turbulence are investigated based on three-dimensional gyrofluid simulation. The focus is on the back reaction of the self-generated zonal flows (ZFs) on the ambient turbulence through nonlinear mode coupling. Detailed spectral analyses evidently show that the radial wave-number spectra of the ITG-ZF turbulence is characterized by an exponential-law scaling, which is deformed from the usual Kolmogorov-like power law by the back reaction of the ZFs. These results are qualitatively in agreement with a theoretical prediction [Gurcan et al., Phys. Rev. Lett. 102, 255002 (2009)] and fairly match with the experimental observation of the density fluctuation spectrum [Hennequin et al., Plasma Phys. Controlled Fusion 46, B121 (2004)]. The generality of such spectral characteristics in drift wave turbulence with large-scale coherent structures is discussed. (C) 2010 American Institute of Physics. [doi:10.1063/1.3456521]