Turbulent current drive mechanisms

McDevitt, Christopher J.; Tang, Xian-Zhu; Guo, Zehua

doi:10.1063/1.4996222

Cited by 13 publications

(28 citation statements)

References 24 publications

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“…(9), the residual turbulent flux can be written as It should be mentioned that although both the turbulent flux and source seem to diverge as approaching to the rational surface, i.e., | ∥ | → 0 ( e 2 → ∞), the factor of exponential convergence exp(− e 2 ) will regularize the magnitude of the turbulent flux and source. This has been discussed in Ref 20…”

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confidence: 88%

Intrinsic current driven by electromagnetic electron drift wave turbulence in the tokamak pedestal region

He¹,

Wang²,

Zhuang³

2019

Plasma Phys. Control. Fusion

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The local intrinsic parallel current density driven by electron drift wave (DW) turbulence including electromagnetic (EM) effects is analytically studied. The scalings of the ratios of intrinsic current density driven by residual turbulent flux and by turbulent source to the bootstrap current density with electron density and temperature are predicted to be e 3 4 ⁄ i e ⁄ and e i e ⁄ , respectively. Based on the typical parameters in DIII-D pedestal region, the local intrinsic current density driven by both the residual turbulent flux and the turbulent source is negligible. However, despite the negligible turbulent source driven current, the residual turbulent flux driven local intrinsic current density by EM DW turbulence can reach about 66% of the bootstrap current density for ITER pedestal parameters due to much lower collisionality in ITER than in DIII-D. Moreover, the contributions from adiabatic ES parts, non-adiabatic ES parts and non-adiabatic EM parts of the plasma response to electromagnetic fluctuations are analyzed. It is found that there exists strong cancelation between non-adiabatic ES response and the non-adiabatic EM response for the ITER pedestal case, and thus the kinetic stress contributed by the adiabatic ES response of parallel electron pressure dominates the intrinsic current drive. This is different from the ES electron DW case. Therefore, the EM effects on turbulence driven intrinsic current density should be carefully considered in the future reactor with high ratio of electron pressure to the magnetic pressure and steep pressure profile. 2

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confidence: 88%

Intrinsic current driven by electromagnetic electron drift wave turbulence in the tokamak pedestal region

He¹,

Wang²,

Zhuang³

2019

Plasma Phys. Control. Fusion

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“…5 The current driven by turbulence has been discussed in detail using the analytical and numerical approaches. 3,4,[6][7][8][9][10] It has been shown by S. -I. Itoh and K. Itoh firstly with a slab model. 6 Driftwave fluctuations drive a net current when k is finite, where k is the averaged parallel wave number over the spectrum .…”

Section: Introductionmentioning

confidence: 93%

“…The spontaneous variation of electron momentum provides a current source which corrugates the current density profile and has significant impacts on the generation of the plasma self-driven mean current. 3,4 The current induced by turbulence affects the MHD instabilities which can provide a way to study the interaction between the turbulence and the MHD instabilities.…”

Section: Introductionmentioning

confidence: 99%

“…One is the divergence of the electron parallel momentum flux which is produced by the magnetic flutter, and the other is the beating of the parallel electric field fluctuations with the electron density fluctuations. 7 In the electrostatic turbulence, three mechanisms of the turbulence driven current have been analyzed by McDevitt, 3 namely, (1) the electron residual stress, which causes a current redistribution, (2) the turbulent acceleration, which is the momentum exchange between ions and electrons and causes a net current, (3) the turbulence induced resonant electron scattering, which leads to the equilibrium between the trapped and passing electrons, 11 similar to the mechanism of the bootstrap current. 1,2 Electromagnetic simulations show that the dynamo current density has spike structures near the rational surface.…”

Section: Introductionmentioning

confidence: 99%

“…The electron momentum flux and turbulent electron-ion momentum exchange have been analyzed for identifying the current driven mechanisms, to draw the connection with the theoretical analyses. 3 The remainder of this paper is organized as follows. In Sec.…”

Section: Introductionmentioning

confidence: 99%

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Gyrokinetic simulations of electric current generation in ion temperature gradient driven turbulence

Chen,

Lu,

Cai

et al. 2021

Preprint

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Gyrokinetic simulations in the collisionless limit demonstrate the physical mechanisms and the amplitude of the current driven by turbulence. Simulation results show the spatio-temporal variation of the turbulence driven current and its connection to the divergence of the Reynolds stress and the turbulence acceleration. Fine structures (a few ion Larmor radii) of the turbulence induced current are observed near the rational surfaces with the arbitrary wavelength solver of the quasi-neutrality equation. The divergence of the Reynolds stress plays a major role in the generation of these fine structures. The so-called "spontaneous" current is featured with large local magnitude near the rational surfaces.

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On turbulence driven stationary electric currents in a tokamak

et al. 2018

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This paper investigates the influence of turbulent dynamics on the neo-classical equilibrium in a tokamak, with an emphasis on the turbulence driven stationary electric current. The neo-classical solution is evaluated using the Hirschmann-Sigmar formalism, in which the turbulent dynamics enter as a forcing term. The latter forcing terms are evaluated through time averages of gyro-kinetic turbulence simulations and are linked with the velocity non-linearity in the gyro-kinetic equation. The time averaged turbulent forcing terms connected with the velocity non-linearity provide a non-negligible current drive, despite being a correction of second order in the normalized Larmor radius. For ITG turbulence, the force exerted due to the heat flux balance is the dominant contribution to the current. The parallel fluctuations of electron density/temperature and the electrostatic potential drive the majority of the current, which is in magnitude comparable to the bootstrap current in the kinetic cyclone base case and increases the total current by a few percent in cases with an experimentally relevant heat flux. An up-down symmetry breaking mechanism is required for turbulent current drive, which is provided in this study by a background rotation or rotation gradient. Consequently, the current is nearly linear in the plasma rotation or its gradient.

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Turbulent current drive mechanisms

Cited by 13 publications

References 24 publications

Intrinsic current driven by electromagnetic electron drift wave turbulence in the tokamak pedestal region

Intrinsic current driven by electromagnetic electron drift wave turbulence in the tokamak pedestal region

Gyrokinetic simulations of electric current generation in ion temperature gradient driven turbulence

On turbulence driven stationary electric currents in a tokamak

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