Microtearing turbulence and heat transport

The microtearing modes and the heat transport in tokamaks are discussed. A model, in which the non linear action of modes (on a given Fourier component of the perturbed distribution function) is represented by a velocity dependent diffusion coefficient operator, is applied. The aim of the study is a better understanding of the process (in collisionless regimes) in which microtearing modes are driven unstable. The results show that it can be obtained under the effect of the radial diffusion they induce in non linear regimes where magnetic islands overlap. Moreover, the bounds obtained on the heat transport coefficient do not allow to neglect such a turbulence