Dynamics of the L - H transition

Abstract

Dynamics of the L - H and H - L transitions are addressed numerically. The focus is on the power level slightly above the threshold. Therefore, at the edge the electric field is assumed to be neoclassical and the toroidal rotation to be damped by anomalous viscosity and inertia. The diffusion coefficient depends on the shear of the electric field. For a given set of boundary conditions, the phenomenon of `dithering' emerges. In contrast, if the power on the separatrix significantly exceeds the threshold the L - H transition occurs directly, without falling into the dithering regime.