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Title: Comparison of multiscale analysis models applied to zonal flow generation in ion-temperature-gradient mode turbulence

Abstract

During the past years the understanding of the multiscale interaction problems have increased significantly. However, at present there exists a range of different analytical models for investigating multiscale interactions and hardly any specific comparisons have been performed among these models. In this work, two different models for the generation of zonal flows from ion-temperature-gradient (ITG) background turbulence are discussed and compared. The methods used is the coherent mode coupling model and the wave kinetic equation model (WKE). It is shown that the two models qualitatively give the same results even though the assumption on the spectral difference is used in the WKE approach.

Authors:
;  [1]
  1. Department of Fundamental Energy Science, Graduate School of Energy Science, Kyoto University, Gokasho, Uji, Kyoto 611-0011 (Japan)
Publication Date:
OSTI Identifier:
20960096
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physics of Plasmas; Journal Volume: 14; Journal Issue: 1; Other Information: DOI: 10.1063/1.2432050; (c) 2007 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; COMPARATIVE EVALUATIONS; ION TEMPERATURE; KINETIC EQUATIONS; PLASMA; TEMPERATURE GRADIENTS; TURBULENCE

Citation Formats

Anderson, J., and Kishimoto, Y.. Comparison of multiscale analysis models applied to zonal flow generation in ion-temperature-gradient mode turbulence. United States: N. p., 2007. Web. doi:10.1063/1.2432050.
Anderson, J., & Kishimoto, Y.. Comparison of multiscale analysis models applied to zonal flow generation in ion-temperature-gradient mode turbulence. United States. doi:10.1063/1.2432050.
Anderson, J., and Kishimoto, Y.. Mon . "Comparison of multiscale analysis models applied to zonal flow generation in ion-temperature-gradient mode turbulence". United States. doi:10.1063/1.2432050.
@article{osti_20960096,
title = {Comparison of multiscale analysis models applied to zonal flow generation in ion-temperature-gradient mode turbulence},
author = {Anderson, J. and Kishimoto, Y.},
abstractNote = {During the past years the understanding of the multiscale interaction problems have increased significantly. However, at present there exists a range of different analytical models for investigating multiscale interactions and hardly any specific comparisons have been performed among these models. In this work, two different models for the generation of zonal flows from ion-temperature-gradient (ITG) background turbulence are discussed and compared. The methods used is the coherent mode coupling model and the wave kinetic equation model (WKE). It is shown that the two models qualitatively give the same results even though the assumption on the spectral difference is used in the WKE approach.},
doi = {10.1063/1.2432050},
journal = {Physics of Plasmas},
number = 1,
volume = 14,
place = {United States},
year = {Mon Jan 15 00:00:00 EST 2007},
month = {Mon Jan 15 00:00:00 EST 2007}
}
  • During the past years the understanding of the multi scale interaction problems have increased significantly. However, at present there exists a flora of different analytical models for investigating multi scale interactions and hardly any specific comparisons have been performed among these models. In this work two different models for the generation of zonal flows from ion-temperature-gradient (ITG) background turbulence are discussed and compared. The methods used are the coherent mode coupling model and the wave kinetic equation model (WKE). It is shown that the two models give qualitatively the same results even though the assumption on the spectral difference ismore » used in the (WKE) approach.« less
  • The present work investigates the direct interaction of sheared mean flow with zonal flows (ZFs) and the effect of parallel ion motion on ZF generation in ion-temperature-gradient (ITG) background turbulence. An analytical model for the direct interaction of sheared mean flows with zonal flows is constructed. The model used for the toroidal ITG driven mode is based on the equations for ion continuity, ion temperature and parallel ion motion, whereas the ZF evolution is described by the vorticity equation. The behavior of the ZF growth rate and real frequency is examined for typical tokamak parameters. It is shown that inmore » general the zonal flow growth rate is suppressed by the presence of a sheared mean flow. In addition, with parallel ion motion effects the ZFs become more oscillatory for increasing {eta}{sub i}(=L{sub n}/L{sub Ti}) value.« less
  • The role of parallel ion motion for zonal flow generation in ion-temperature-gradient (ITG) mode turbulence is investigated with focus on the effects of acoustic modes and toroidicity on the zonal flow. One possible reason for the weak suppression of ITG turbulence by zonal flows found in experiments in the Columbia Linear Machine [Phys. Plasmas 13, 055905 (2006)] might be due to the small toroidicity ({epsilon}{sub n}=2L{sub n}/R) in the experiment. The zonal flow is often directly dependent on the ITG mode and the coupling of zonal flow to acoustic modes and hence is directly affected by any change of themore » relevant parameters. The model consists of the continuity, temperature, and parallel ion momentum equations for the ITG turbulence. The zonal flow time evolution is described by a Hasegawa-Mima-like equation, and a fifth-order zonal flow dispersion relation is derived. The results are interpreted in terms of quality of zonal flows, i.e., the ratio of growth rate and real frequency (Q={omega}{sup IM}/{omega}{sup RE}). It is found that the quality of the zonal flow rapidly decreases with decreasing toroidicity.« less
  • Collisionless trapped ion modes (CTIMs) turbulence exhibits a rich variety of zonal flow physics. The coupling of CTIMs with shear flow driven by the Kelvin-Helmholtz (KH) instability has been investigated. The work explores the parametric excitation of zonal flow modified by wave-particle interactions leading to a new type of resonant low-frequency zonal flow. The KH-CTIM interaction on zonal flow growth and its feedback on turbulence is investigated using semi-Lagrangian gyrokinetic Vlasov simulations based on a Hamiltonian reduction technique, where both fast scales (cyclotron plus bounce motions) are gyro-averaged.
  • Collisionless time evolution of zonal flows in ion and electron temperature gradient turbulence in toroidal plasmas is investigated. The responses of the zonal-flow potential to the initial perturbation and to the turbulence source are determined from the gyrokinetic equations combined with the Poisson equation, A novel gyrofluid model is presented, which properly describes the zonal-flow time evolution and reproduces the same residual zonal-flow levels as predicted by the gyrokinetic model.