Effects of sawtooth heat pulses on edge flows and turbulence in a tokamak plasma

Abstract The enhancements of the edge zonal flows, radial electric field and turbulence are observed in ECRH heated plasmas [K. J. Zhao et al., Nuclear Fusion 2013, 083011]. In this paper, the effects of sawtooth heat pulses on the flows and turbulence are presented. These experiments are performed using multiple Langmuir probe arrays in the edge plasmas of the HL-2A tokamak. The edge zonal flows, radial electric fields, and turbulence are all enhanced by sawteeth. The propagation of the zonal flow and turbulence intensities is also observed. The delay time of the maximal intensity of the electric fields, zonal flows, and turbulence with respect to the sawtooth crashes is estimated as ∼ 1 ms and comparable to that of the sawtooth-triggered I-phases. Not only the zonal flows but also the radial electric fields lag behind the turbulence. Furthermore, the intensities of both the zonal flows and electric field nearly linearly increase/decrease with the increase/decrease of the turbulence intensity. A double source predator-prey model analysis suggests that a relatively strong turbulence source may contribute to the dominant zonal flow formation during sawtooth cycles.