title: Gyrokinetic theory of turbulent acceleration of parallel rotation in tokamak plasmas.
abstract: A mechanism for turbulent acceleration of parallel rotation is discovered using gyrokinetic theory. This new turbulent acceleration term cannot be written as a divergence of parallel Reynolds stress. Therefore, turbulent acceleration acts as a local source or sink of parallel rotation. The physics of turbulent acceleration is intrinsically different from the Reynolds stress. For symmetry breaking by positive intensity gradient, a positive turbulent acceleration, i.e., cocurrent rotation, is predicted. The turbulent acceleration is independent of mean rotation and mean rotation gradient, and so constitutes a new candidate for the origin of spontaneous rotation. A quasilinear estimate for ion temperature gradient turbulence shows that the turbulent acceleration of parallel rotation is explicitly linked to the ion temperature gradient scale length and temperature ratio Ti0/Te0. Methods for testing the effects of turbulent parallel acceleration by gyrokinetic simulation and experiment are proposed.
authors.affiliation: CEEE, Huazhong University of Science and Technology, Wuhan, Hubei 430074, China. luwang@hust.edu.cn
authors.forename: Lu
authors.initials: L
authors.lastname: Wang
authors.forename: P H
authors.initials: PH
authors.lastname: Diamond