THE RESISTIVE INTERCHANGE CONVECTION IN THE EDGE OF TOKAMAK PLASMAS

Theoretical results are presented addressing the behaviour of plasmas outside the separatrix i.e. in the region where the magnetic field lines do not form closed magnetic surfaces. The resistive interchange model is used to describe self-consistently the generation of poloidal (or toroidal) flow and the onset of ELMs, which appear as bubbles of increased density (or higher temperature). In addition, the decrease of the turbulent transport processes as the velocity of the flow increases and its connection with the LH transition are discussed. The linear theory of stability is applied and complemented by a full numerical simulation of the two-dimensional nonlinear equations. Analytic solutions for asymptotically small parameters in the nonlinear model are derived and used for the explanation of the numerical results. Semi-phenomenological turbulence balance equaitons for the resistive interchange convection are presented as well. Finally, these results are applied for the explanation of existing experiments.