Size Scaling and Nondiffusive Features of Electron Heat Transport in Multi-Scale Turbulence

We report recent results from global gyrokinetic particle simulations of the collisionless trapped electron mode (CTEM) turbulence, turbulent momentum transport, and turbulent transport in the reverse shear toroidal plasmas. The study of CTEM turbulence shows that the presence of mesoscale structures drives a nondiffusive component in the electron heat flux due to the weak nonlinear detuning of the precessional resonance that excites the linear instability. The simulation of turbulent momentum transport finds conductive, pinch, and residual momentum fluxes. The study of turbulent transport in the reverse shear toroidal plasmas shows that, due to the turbulence spreading, the electrostatic drift wave turbulence itself does not support either linear or nonlinear mechanism for the formation of internal transport barriers in the reversed magnetic shear when min q crossing an integer.