Numerical study of drift wave turbulence with simple models for wave–wave nonlinear coupling

Scattering experiments in tokamaks show a broad drift wave frequency spectrum Δω/ω∼O(1) at fixed wavenumbers indicating a strong turbulent state with unstable drift modes strongly decorrelated at a rate Δω by nonlinear wave–wave coupling to stable modes. In this paper a two-dimensional study of homogeneous stationary drift wave turbulence with simple models of the wave–wave coupling is described. It shows that linearly driven-damped stationary states exist and demonstrates that approximate weak coupling theories based on the direct interaction approximation (DIA) can provide a faithful and practical description of the turbulence. In addition, it is found that simple models which include nonlinear E×B as well as nonlinear polarization drift coupling are in rough agreement with the experimental turbulence levels, transport coefficients, and decorrelation rates.