Description of turbulent convection in a plasma with the help of interacting Lorentz oscillators

A four-field model is proposed that describes turbulent plasma convection inside the separatrix during the L-H transition. It is shown that the Braginskii four-field hydrodynamic equations, which describe fluctuations of the electron and ion temperatures, plasma density, and electrostatic potential in tokamak edge plasmas, can be reduced to three Lorentz-like systems of equations coupled through the equation for the kinetic energy of the fluctuations, i.e., to a four-field edge turbulent layer model describing the nonlinear dynamics of convective cells in the presence of a sheared flow. For three coupled oscillators, the critical pressure gradient corresponding to transitions to both L-and H-modes is found to be much lower than that for an individual oscillator, which describes turbulent convection driven by fluctuations of one type. The edge turbulent layer model makes it possible to describe the formation of a transport barrier inside the separatrix during the L-H transition; calculate heat and particle fluxes via ion and electron channels; and, in combination with the transport code for a core plasma, compute the auxiliary heating power required for a transition to the H-mode.