Role of trapped electron mode turbulence in internal transport barrier control in the Alcator C-Mod Tokamak

Ernst, D. R.; Bonoli, P.; Catto, Peter J.; Dorland, W.; Fiore, C. L.; Granetz, R.; Greenwald, M.; Hubbard, A.E.; Porkoláb, M.; Redi, M. H.; Rice, J.E.; Zhurovich, K.

doi:10.1063/1.1705653

Cited by 154 publications

(162 citation statements)

References 56 publications

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“…We also used comparisons with the analytical results from both theories to verify and demonstrate the accuracy of the gyrokinetic simulation code GS2 in the parameter regimes of astrophysical interest. We note that although our tests are linear, GS2 has already been used extensively for nonlinear turbulence problems in the fusion research (e.g., Dorland et al 2000;Jenko et al 2000Rogers et al 2000;Candy et al 2004;Ernst et al 2004), and a program of nonlinear astrophysical turbulence simulations is currently underway.…”

Section: Resultsmentioning

confidence: 99%

Astrophysical Gyrokinetics: Basic Equations and Linear Theory

Howes

Cowley

Dorland

et al. 2006

ApJ

304

669

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Magnetohydrodynamic (MHD) turbulence is encountered in a wide variety of astrophysical plasmas, including accretion disks, the solar wind, and the interstellar and intracluster medium. On small scales, this turbulence is often expected to consist of highly anisotropic fluctuations with frequencies small compared to the ion cyclotron frequency. For a number of applications, the small scales are also collisionless, so a kinetic treatment of the turbulence is necessary. We show that this anisotropic turbulence is well described by a low-frequency expansion of the kinetic theory called gyrokinetics. This paper is the first in a series to examine turbulent astrophysical plasmas in the gyrokinetic limit. We derive and explain the nonlinear gyrokinetic equations and explore the linear properties of gyrokinetics as a prelude to nonlinear simulations. The linear dispersion relation for gyrokinetics is obtained, and its solutions are compared to those of hot-plasma kinetic theory. These results are used to validate the performance of the gyrokinetic simulation code GS2 in the parameter regimes relevant for astrophysical plasmas. New results on global energy conservation in gyrokinetics are also derived. We briefly outline several of the problems to be addressed by future nonlinear simulations, including particle heating by turbulence in hot accretion flows and in the solar wind, the magnetic and electric field power spectra in the solar wind, and the origin of small-scale density fluctuations in the interstellar medium.

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Section: Resultsmentioning

confidence: 99%

Astrophysical Gyrokinetics: Basic Equations and Linear Theory

Howes

Cowley

Dorland

et al. 2006

ApJ

304

669

View full text Add to dashboard Cite

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“…66,[82][83][84][85][86][87][88][89][90][91][92][93][94] Many other validation studies have assessed the sensitivity of 16 inputs but not explicitly presented the results in the form shown in Fig. 5.…”

Section: Building Robust Local Turbulent Transport Validation Metmentioning

confidence: 99%

Validation metrics for turbulent plasma transport

Holland

2016

Physics of Plasmas

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Developing accurate models of plasma dynamics is essential for confident predictive modeling of current and future fusion devices. In modern computer science and engineering, formal verification and validation processes are used to assess model accuracy and establish confidence in the predictive capabilities of a given model. This paper provides an overview of the key guiding principles and best practices for the development of validation metrics, illustrated using examples from investigations of turbulent transport in magnetically confined plasmas. Particular emphasis is given to the importance of uncertainty quantification and its inclusion within the metrics, and the need for utilizing synthetic diagnostics to enable quantitatively meaningful comparisons between simulation and experiment. As a starting point, the structure of commonly used global transport model metrics and their limitations is reviewed. An alternate approach is then presented, which focuses upon comparisons of predicted local fluxes, fluctuations, and equilibrium gradients against observation. The utility of metrics based upon these comparisons is demonstrated by applying them to gyrokinetic predictions of turbulent transport in a variety of discharges performed on the DIII-D tokamak [J. L. Luxon, Nucl. Fusion 42, 614 (2002)], as part of a multi-year transport model validation activity.

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“…In some of these cases, nonlinear wavenumber transfers can increase or cause drive, 26,27 while in other cases zonal flow effects decrease drive. 28,29 In order to avoid the pitfalls of relying too heavily on linear stability calculations in forming conclusions on turbulence characteristics, it is useful to perform turbulent simulations and diagnose them with energy dynamics analyses. Energy dynamics analyses track energy input into turbulent fluctuations and energy dissipation out of them.…”

Section: Introductionmentioning

confidence: 99%

Energy dynamics in a simulation of LAPD turbulence

et al. 2012

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Energy dynamics calculations in a 3D fluid simulation of drift wave turbulence in the linear Large Plasma Device [W. Gekelman et al., Rev. Sci. Instrum. 62, 2875] illuminate processes that drive and dissipate the turbulence. These calculations reveal that a nonlinear instability dominates the injection of energy into the turbulence by overtaking the linear drift wave instability that dominates when fluctuations about the equilibrium are small. The nonlinear instability drives flutelike (k k ¼ 0) density fluctuations using free energy from the background density gradient. Through nonlinear axial wavenumber transfer to k k 6 ¼ 0 fluctuations, the nonlinear instability accesses the adiabatic response, which provides the requisite energy transfer channel from density to potential fluctuations as well as the phase shift that causes instability. The turbulence characteristics in the simulations agree remarkably well with experiment. When the nonlinear instability is artificially removed from the system through suppressing k k ¼ 0 modes, the turbulence develops a coherent frequency spectrum which is inconsistent with experimental data. This indicates the importance of the nonlinear instability in producing experimentally consistent turbulence. V C 2012 American Institute of Physics. [http://dx

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Role of trapped electron mode turbulence in internal transport barrier control in the Alcator C-Mod Tokamak

Cited by 154 publications

References 56 publications

Astrophysical Gyrokinetics: Basic Equations and Linear Theory

Astrophysical Gyrokinetics: Basic Equations and Linear Theory

Validation metrics for turbulent plasma transport

Energy dynamics in a simulation of LAPD turbulence

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