On the normalization of transport from ITG modes

Journal article, 2016

We have analyzed the interplay of ITG turbulence and zonal flows as derived by the reductive perturbation method. Not surprisingly, the overall transport level depends strongly on the physics description of ITG modes. In particular, the fluid resonance turns out to play a dominant role for the excitation of zonal flows. This is the mechanism recently found to lead to the L-H transition and to the nonlinear Dimits upshift in transport code simulations. It is important that we have here taken the nonlinear temperature dynamics from the Reynolds stress as the convected diamagnetic flow. This has turned out to be the most relevant effect as found in transport simulations of the L-H transition, internal transport barriers, and Dimits shift.