Generation of large-scale structures by strong drift turbulence

The previously existing quasilinear theory of the generation of a large-sca le radial electric field by small-scale drift turbulence in a plasma is gen eralized for the case of strong turbulence which is usually observed in exp eriments. The geostrophic equation (i.e., the reduced Charney-Hasegawa-Mima equation) is used to construct a systematic theory in the two-scale direct interaction approximation. It is shown that, as in the quasilinear case, d rift turbulence results in a turbulent viscosity effect and leads to the re normalization of the Poisson bracket in the Charney-Hasegawa-Mima equation. It is found that, for strong drift turbulence, the viscosity coefficient i s represented as a sum of two parts, which are comparable in magnitude. As in quasilinear theory, the first part is determined by the second-order cor relation functions of the turbulent field and is always negative. The secon d part is proportional to the third-order correlation functions, and the si gn of its contribution to the turbulent viscosity coefficient depends stron gly on the turbulence spectrum. The turbulent viscosity coefficient is calc ulated numerically for the Kolmogorov spectra, which characterize the inert ial interval of the drift turbulence. (C) 2001 MAIK "NaukalInterperiodica".