I2-S3 · Global structure of ITG turbulence-zonal mode system in tokamak plasmasMiyato, Naoaki1) Abstract Using a global Landau fluid code in toroidal geometry, an electromagnetic ion temperature gradient (ITG) driven turbulence-zonal mode system in tokamak plasmas is investigated. Two different types of zonal flows, i.e. stationary zonal flows in a low q (safety factor) region and oscillatory ones in a high q 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. As a result of the different behaviour of the zonal flows, the tokamak plasma divides into the zonal flow dominant region and the turbulent region.
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