Gyro-kinetic study of Rosenbluth-Hinton flow for fusion reactor plasmas

Zonal flow, an axisymmetric potential fluctuation driven by turbulent Reynolds stress, takes a key role of turbulence regulation with its flow shear. It gets damped by collisionless process, but to a non-zero value called the residual zonal flow level due to polarization shielding. Previous studies were done assuming the Maxwellian equilibrium distribution. In this study, we investigate the residual zonal flow for the Slowing down distribution function using modern gyro-kinetic approach. We find that zonal flow for Slowing down case remains at a higher level than that for equivalent Maxwellian case in the intermediate wavelength range, k_r · ρ_θi ∼ 1. (authors)