Understanding of anomalous transport in high temperature plasma is a crucial issue in nuclear fusion research. Ion temperature gradient driven drift wave (ITG) is a possible candidate for anomalous ion heat transport. The gyro-kinetic simulations of ITG turbulence demonstrate that zonal flows play a crucial role in regulating drift wave turbulence and the level of anomalous transport[1]. The theoretical explanation for the generation of zonal flow is proposed based on parametric instability in shearless slab geometry[2,3]. Simulations in such a simplified drift wave system were performed[4], however, parameter dependences were not examined systematically. In this paper, we perform the simulation study of universal drift wave turbulence and investigate the convective cell dynamics in detail. Simulation results show that convective cell is nonlinearly excited where the main contribution comes from zonal flow component. In the collisionless limit, drift wave energy is larger than zonal flow energy. However, if we introduce the large ion-ion collision effect, then the inequality changes. In both cases no saturated state is attained. This is attributed from the fact that strong instability source exists in the short wave length region without a sufficient energy sink. In the case of ITG turbulence, the instability source exists in the long wavelength region and there is energy sink in the short wavelength region. Our simulation results may not apply to ITG theory directly[2]. Nevertheless there remains a question that cascade processes play a role in turbulence dynamics. Because the zonal flow is excited by inverse cascade of drift waves and can regulate the component of drift wave turbulence. Further analysis is reported.

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