Physical model of L- and H-modes in a tokamak

A model of collective processes in tokamak plasmas is formulated, its physical basis is given. The structures of particles energy fluxes are analysed, conditions for the existence and the absence of a pinch in the particle flux are are discussed. A new diffusion coefficient for a strongly-turbulent plasma is obtained. This coefficient allows one to explain the scaling law for the L-mode. A scenario for the transition to the L- and H-modes is proposed. A scenario for the transition to the L- and H-modes is proposed. It is confirmed by the results of numerical simulation. 9 refs.; 6 figs