ELECTRON-TEMPERATURE FLUCTUATIONS IN DRIFT-RESISTIVE BALLOONING TURBULENCE

Three-dimensional nonlinear simulations of collisional plasma turbulen ce are presented to model the behavior of the edge region of tokamak d ischarges. Previous work is extended by including electron temperature fluctuations (T) over tilde(e). The basic paradigm that turbulence an d transport are controlled by resistive ballooning modes in low temper ature plasma and nonlinearly driven drift wave turbulence in higher te mperature regimes persists in the new system. Parallel thermal conduct ion strongly suppresses the ability of the electron temperature gradie nt del T-e to drive the turbulence and transport everywhere except the very low temperature edge of the resistive ballooning regime. As a co nsequence, over most of the resistive ballooning regime only the densi ty gradient drives the turbulence and the temperature fluctuations are convected as a passive scalar. In the drift wave regime only the dens ity gradient acts to drive the nonlinear instability and the temperatu re fluctuations have a relatively strong stabilizing influence on the turbulence due to an enhanced damping of density and potential fluctua tions resulting from local electron heating. (C) 1997 American Institu te of Physics.