Study of nonlinear dynamics among zonal flow, GAM, and turbulence on the HL-2A strongly heated L-mode plasmas

Experiments to directly measure the nonlinear energy exchange and interaction among turbulence, zonal flows, and GAMs were carried out on the HL-2A tokamak at the Southwestern Institute of Physics (SWIP) in China. The turbulent kinetic energy was clearly shown to transfer from turbulence with intermediate frequencies (20-60 kHz) to zonal flows (0-5 kHz) and GAMs ($\sim $10 kHz) and to turbulent fluctuations with high frequencies ($>$60 kHz), which also indicates that zonal flows and GAMs compete for turbulent energy as the heating power increased. The turbulent Reynolds stress $\left\langle {\tilde {v}_r \tilde {v}_{pol} } \right\rangle $ profiles were shown consistent with the time-averaged poloidal velocity profiles inferred by time-delay estimation. Other microphysical quantities together with the macro statistical results form a consistent picture that turbulent vortices mediate the energy, momentum, particle transport, and the formation of sheared flows in the edge of plasmas.