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Miyato, Naoaki; Kishimoto, Yasuaki; Li, J.*
Plasma Physics and Controlled Fusion, 48(5A), p.A335 - A340, 2006/05
Times Cited Count：26 Percentile：64.63(Physics, Fluids & Plasmas)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.
Idomura, Yasuhiro; Tokuda, Shinji; Kishimoto, Yasuaki
Nuclear Fusion, 45(12), p.1571 - 1581, 2005/12
Times Cited Count：39 Percentile：74.86(Physics, Fluids & Plasmas)Using a global gyrokinetic toroidal particle code, the toroidal electron temperature gradient driven (ETG) turbulence is studied in positive and reversed shear tokamaks. In the nolinear turbulent state, the ETG turbulence in the positive and reversed shear configurations show quite different structure formations. In the positive shear configuration, the ETG turbulence is dominated by streamers which have a ballooning type structure, and the electron temperature 
profile is quickly relaxed to the marginally stable state in a turbulent time scale. In the reversed shear configuration, quasi-steady zonal flows are produced in the regative shear region, while the positive shear region is characterized by streamers. Accordingly, the electron thermal diffusivity 
has a gap structure across the 
surface, and the gradinet is sustained above the marginal value for a long time in the quasi-steady phase. The results suggest a stiffness of the profile in positive shear tokamaks, and a possibility of the Te transport barrier in reversed shear tokamaks.
Kishimoto, Yasuaki; Idomura, Yasuhiro; Li, J.
Purazuma, Kaku Yugo Gakkai-Shi, 79(5), p.478 - 488, 2003/05
This is a collection of review article related to the "Multiple Time and Spatial Scale Plasma Simulation" of various fields including fundamental research area of self-organization, magnetic and laser fusion field, space and astrophysics field where a plasma plays an essential roles.
