Kinetic simulation of ηi modes and transport in tokamaks

The Toroidal Particle Code (TPC) is used to examine ηi modes and transport in a toroidal plasma. Kinetic ion and adiabatic electron responses in a toroidal metric were used. Simulations involving both multiple and single toroidal Fourier modes were performed. The measured ion heat diffusivity χi from the simulations is of similar magnitude and radial variation as that seen in tokamak experiments. The multiple toroidal mode runs show behavior similar to the single toroidal mode runs, establishing the primary importance of toroidicity-induced coupling of rational surfaces through the poloidal mode number over any toroidal mode coupling. In all runs the presence of a global mode, together with the formation of radially extended open-quotes streamersclose quotes which decrease in extent after saturation suggests a possible mechanism for transport. The temperature profile follows a slow self-similar relaxation as it approaches marginal stability, but maintains the instability that drives the steady state heat flux. This state is a self-organized critical state, with any change in local temperature causing a change in the wave activity and transport, resulting in a globally smooth temperature profile. This behavior yields a radially increasing χi. The size of the observed open-quotes streamersclose quotes in the simulations suggests Bohm scaling