The dynamics of secondary large-scale structures in electron-temperature-gradient （ETG） turbulence is investigated based on gyrofluid simulations in sheared slab geometry. It is found that structural bifurcation to ...The dynamics of secondary large-scale structures in electron-temperature-gradient （ETG） turbulence is investigated based on gyrofluid simulations in sheared slab geometry. It is found that structural bifurcation to zonal flow dominated or streamer-like states depends on the spectral anisotropy of turbulent ETG fluctuation, which is governed by the magnetic shear. The turbulent electron transport is suppressed by enhanced zonal flows. However, it is still low even if the streamer is formed in ETG turbulence with strong shears. It is shown that the low transport may be related to the secondary excitation of poloidal long-wavelength mode due to the beat wave of the most unstable components or a modulation instability. This large-scale structure with a low frequency and a long wavelength may saturate, or at least contribute to the saturation of ETG fluctuations through a poloidal mode coupling. The result suggests a low fluctuation level in ETG turbulence.展开更多
An improved three-field gyrofluid model is proposed to numerically simulate ion-scale turbulence in tokamak plasmas,which includes the nonlinear evolution of perturbed electrostatic potential,parallel ion velocity and...An improved three-field gyrofluid model is proposed to numerically simulate ion-scale turbulence in tokamak plasmas,which includes the nonlinear evolution of perturbed electrostatic potential,parallel ion velocity and ion pressure with adiabatic electron response.It is benchmarked through advancing a gyrofluid toroidal global(GFT G)code as well as the local version(GFT L),with the emphasis of the collisionless damping of zonal flows.The nonlinear equations are solved by using Fourier decomposition in poloidal and toroidal directions and semi-implicit finite difference method along radial direction.The numerical implementation is briefly explained,especially on the periodic boundary condition in GFT L version.As a numerical test and also practical application,the nonlinear excitation of geodesic acoustic mode(GAM),as well as its radial structure,is investigated in tokamak plasma turbulence.展开更多
基金supported in part by the National Natural Science Foundation of China(Nos.10135020 and 10575032)
文摘The dynamics of secondary large-scale structures in electron-temperature-gradient （ETG） turbulence is investigated based on gyrofluid simulations in sheared slab geometry. It is found that structural bifurcation to zonal flow dominated or streamer-like states depends on the spectral anisotropy of turbulent ETG fluctuation, which is governed by the magnetic shear. The turbulent electron transport is suppressed by enhanced zonal flows. However, it is still low even if the streamer is formed in ETG turbulence with strong shears. It is shown that the low transport may be related to the secondary excitation of poloidal long-wavelength mode due to the beat wave of the most unstable components or a modulation instability. This large-scale structure with a low frequency and a long wavelength may saturate, or at least contribute to the saturation of ETG fluctuations through a poloidal mode coupling. The result suggests a low fluctuation level in ETG turbulence.
基金This work was sup-ported by theGrant-in-Aid fromJapan Society for the Promotion of Science(No.18340186 and 19560828)partly by theNational Science Foundation of China GrantNo.10575032 and by the JSPS-CAS Core University Program(CUP)on Plasma and Nuclear Fusion。
文摘An improved three-field gyrofluid model is proposed to numerically simulate ion-scale turbulence in tokamak plasmas,which includes the nonlinear evolution of perturbed electrostatic potential,parallel ion velocity and ion pressure with adiabatic electron response.It is benchmarked through advancing a gyrofluid toroidal global(GFT G)code as well as the local version(GFT L),with the emphasis of the collisionless damping of zonal flows.The nonlinear equations are solved by using Fourier decomposition in poloidal and toroidal directions and semi-implicit finite difference method along radial direction.The numerical implementation is briefly explained,especially on the periodic boundary condition in GFT L version.As a numerical test and also practical application,the nonlinear excitation of geodesic acoustic mode(GAM),as well as its radial structure,is investigated in tokamak plasma turbulence.
