Tokamak turbulence with stochastic field lines

Abstract
Three-dimensional numerical simulations of ballooning turbulence in a tokamak plasma with stochastic magnetic field lines are presented. Three main features are observed. First, the level of pressure fluctuations decreases in the ergodic layer. Second, this is essentially due to a suppression of large scale structures. Finally, the turbulent heat diffusivity does not decrease in the stochastic layer due to an increase of electric field fluctuations. These observations are in agreement with turbulence measurements on Tore Supra [Equipe Tore Supra, Proceedings, 13th International Conference on Plasma Physics and Controlled Nuclear Fusion, Washington, 1990 (International Atomic Energy Agency, Vienna, 1991), Vol. 1, p. 549].