Study of a drift wave-zonal mode system based on global electromagnetic landau-fluid ITG simulation in toroidal plasmas

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

Using a global Landau fluid code in toroidal geometry, an electromagnetic ion temperature gradient (ITG) driven turbulence-zonal mode system is investigated. Two different types of zonal flows, i.e. stationary zonal flows in a low (safety factor) region and oscillatory ones in a high region which are called geodesic acoustic modes (GAM), are found to be simultaneously excited in a torus. The stationary flows efficiently suppress turbulent transport, while the oscillatory ones weakly affect the turbulence due to their time varying nature. Therefore in the low region where the zonal flows are almost stationary, the zonal flows are dominant over the turbulence. On the other hand, the turbulence is still active in the high region where the zonal flows are oscillatory.