Nonlocal behaviour of zonal flows in tokamak plasmas

Miyato, Naoaki; Kishimoto, Yasuaki; Li, J.*

It is well known that drift wave turbulence such as ion temperature gradient (ITG) driven turbulence and zonal flows nonlinearly generated from it play an important role in anomalous transport in tokamak plasmas. The zonal flows can regulate turbulent transport and trigger formation of transport barriers. In toroidal plasmas there are two kinds of zonal flows. One is stationary zonal flow which is dominant in a low safety factor () region. The other is oscillatory ones appearing in a high region. Global ITG turbulence simulations have shown that the frequencies of the oscillatory zonal flows do not vary continuously with a radius, but the oscillatory zonal flows have the same frequency over a certain radial region. It is considered that the nonlocal behaviour becomes weak for small , where is an ion Larmor radius and is a minor radius of a torus. In this research effects of on the nonlocal behaviour of the zonal flows are investigated by global Landau fluid ITG simulations.