Nonlinear theory of trapped electron temperature gradient driven turbulence in flat density H-mode plasmas

摘要

Ion temperature gradient turbulence based transport models have difficulties reconciling the recent DIII-D H-mode results where the density profile is flat, but (chi)(sub e) > (chi)(sub i) in the core region. In this work, a nonlinear theory is developed for recently discovered ion temperature gradient trapped electron modes propagating in the electron diamagnetic direction. This instability is predicted to be linearly unstable for L(sub Ti)/R (approx lt) (kappa)(sub (theta))(rho)(sub s) (approx lt) (L(sub Ti)/R)(sup 1/4). They are also found to be strongly dispersive even at these long wavelengths, thereby suggesting the importance of the wave-particle-wave interactions in the nonlinear saturation phase. The fluctuation spectrum and anomalous fluxes are calculated. In accordance with the trends observed in DIII-D, the predicted electron thermal diffusivity can be larger than the ion thermal diffusivity. 17 refs., 3 figs.