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Title: Electromagnetic global gyrokinetic simulation of shear Alfven wave dynamics in tokamak plasmas

Abstract

Electromagnetic gyrokinetic simulation in toroidal geometry is developed based on a fluid-kinetic hybrid electron model. The Alfven wave propagation in a fully global gyrokinetic particle simulation is investigated. In the long-wavelength magnetohydrodynamic limit, shear Alfven wave oscillations, continuum damping, and the appearance of the frequency gap in toroidal geometries are demonstrated. Wave propagation across the magnetic field (kinetic Alfven wave) is examined by comparing the simulation results with the theoretical dispersion relation. Furthermore, finite-beta stabilization of the ion temperature gradient mode and the onset of the kinetic ballooning mode are demonstrated.

Authors:
; ;  [1];  [2]
  1. Department of Physics and Astronomy, University of California, Irvine, California 92697 (United States)
  2. (United States)
Publication Date:
OSTI Identifier:
20974932
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physics of Plasmas; Journal Volume: 14; Journal Issue: 4; Other Information: DOI: 10.1063/1.2718908; (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; ALFVEN WAVES; BALLOONING INSTABILITY; DAMPING; DISPERSION RELATIONS; ELECTRON TEMPERATURE; ELECTRONS; GEOMETRY; ION TEMPERATURE; MAGNETIC FIELDS; MAGNETOHYDRODYNAMICS; PLASMA; PLASMA CONFINEMENT; PLASMA SIMULATION; PLASMA WAVES; SHEAR; TEMPERATURE GRADIENTS; TOKAMAK DEVICES; WAVE PROPAGATION

Citation Formats

Nishimura, Y., Lin, Z., Wang, W. X., and Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543. Electromagnetic global gyrokinetic simulation of shear Alfven wave dynamics in tokamak plasmas. United States: N. p., 2007. Web. doi:10.1063/1.2718908.
Nishimura, Y., Lin, Z., Wang, W. X., & Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543. Electromagnetic global gyrokinetic simulation of shear Alfven wave dynamics in tokamak plasmas. United States. doi:10.1063/1.2718908.
Nishimura, Y., Lin, Z., Wang, W. X., and Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543. Sun . "Electromagnetic global gyrokinetic simulation of shear Alfven wave dynamics in tokamak plasmas". United States. doi:10.1063/1.2718908.
@article{osti_20974932,
title = {Electromagnetic global gyrokinetic simulation of shear Alfven wave dynamics in tokamak plasmas},
author = {Nishimura, Y. and Lin, Z. and Wang, W. X. and Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543},
abstractNote = {Electromagnetic gyrokinetic simulation in toroidal geometry is developed based on a fluid-kinetic hybrid electron model. The Alfven wave propagation in a fully global gyrokinetic particle simulation is investigated. In the long-wavelength magnetohydrodynamic limit, shear Alfven wave oscillations, continuum damping, and the appearance of the frequency gap in toroidal geometries are demonstrated. Wave propagation across the magnetic field (kinetic Alfven wave) is examined by comparing the simulation results with the theoretical dispersion relation. Furthermore, finite-beta stabilization of the ion temperature gradient mode and the onset of the kinetic ballooning mode are demonstrated.},
doi = {10.1063/1.2718908},
journal = {Physics of Plasmas},
number = 4,
volume = 14,
place = {United States},
year = {Sun Apr 15 00:00:00 EDT 2007},
month = {Sun Apr 15 00:00:00 EDT 2007}
}
  • The first linear global electromagnetic gyrokinetic particle simulation on the excitation of toroidicity induced Alfven eigenmode (TAE) by energetic particles is reported. It is shown that the long wavelength magnetohydrodynamic instabilities can be studied by the gyrokinetic particle simulation. With an increase in the energetic particle pressure, the TAE frequency moves down into the lower continuum together with an increase in the linear growth rate.
  • Adopting the theoretical framework for the generalized fishbonelike dispersion relation, an extended hybrid magnetohydrodynamics gyrokinetic simulation model has been derived analytically by taking into account both thermal ion compressibility and diamagnetic effects in addition to energetic particle kinetic behaviors. The extended model has been used for implementing an extended version of hybrid magnetohydrodynamics gyrokinetic code (XHMGC) to study thermal ion kinetic effects on Alfvenic modes driven by energetic particles, such as kinetic beta induced Alfven eigenmodes in tokamak fusion plasmas. The XHMGC nonlinear model can be used to address a number of problems, where kinetic treatments of both thermal andmore » supra-thermal plasma components are necessary, as theoretically predicted, or where it is desirable to investigate the phenomena connected with the presence of two supra-thermal particle species with different radial profiles and velocity space distributions.« less
  • A gyrokinetic ion/mass-less fluid electron hybrid model as implemented in the GEM code [Y. Chen and S. E. Parker, J. Comput. Phys. 220, 837 (2007)] is used to study the reverse shear Alfven eigenmodes (RSAE) observed in DIII-D, discharge no. 142111. This is a well diagnosed case with measurement of the core-localized RSAE mode structures and the mode frequency, which can be used to compare with simulations. Simulations reproduce many features of the observation, including the mode frequency up-sweeping in time and the sweeping range. A new algorithmic feature is added to the GEM code for this study. Instead ofmore » the gyrokinetic Poisson equation itself, its time derivative, or the vorticity equation, is solved to obtain the electric potential. This permits a numerical scheme that ensures the E Multiplication-Sign B convection of the equilibrium density profiles of each species cancel each other in the absence of any finite-Larmor-radius effects. These nonlinear simulations generally result in an electron temperature fluctuation level that is comparable to measurements, and a mode frequency spectrum broader than the experimental spectrum. The spectral width from simulations can be reduced if less steep beam density profiles are used, but then the experimental fluctuation level can be reproduced only if a collision rate above the classical level is assumed.« less
  • It is found that the thermal fluctuation level of the shear-Alfven waves in a gyrokinetic plasma is dependent on plasma {beta}((equivalent to)c{sub s}{sup 2}/v{sub A}{sup 2}), where c{sub s} is the ion acoustic speed and v{sub A} is the Alfven velocity. This unique thermodynamic property based on the fluctuation--dissipation theorem is verified in this paper using a new gyrokinetic particle simulation scheme, which splits the particle distribution function into the equilibrium part as well as the adiabatic and nonadiabatic parts. The numerical implication of this property is discussed.