Flux-driven simulations of turbulence collapse

Park, G. Y.; Kim, S. S.; Jhang, Hogun; Diamond, P. H.; Rhee, T.; Xu, X. Q.

doi:10.1063/1.4914841

Cited by 33 publications

(39 citation statements)

References 34 publications

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“…1,2 Efforts to understand the low (L) mode to high (H) mode confinement transition in tokamaks have further increased interest in this topic. [3][4][5][6][7][8][9][10][11] A closely related subject is that of understanding the saturation mechanism for edge and SOL turbulence. 12,13 In addition to contributing to L-H mode transition physics, some models predict that turbulence in the vicinity of the separatrix could be sufficiently large so as to impact the width of the heat flux channel.…”

Section: Introductionmentioning

confidence: 99%

Mean flows and blob velocities in scrape-off layer (SOLT) simulations of an L-mode discharge on Alcator C-Mod

et al. 2016

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Two-dimensional scrape-off layer turbulence (SOLT) code simulations are compared with an L-mode discharge on the Alcator C-Mod tokamak [M. Greenwald, et al., Phys. Plasmas 21, 110501 (2014)]. Density and temperature profiles for the simulations were obtained by smoothly fitting Thomson scattering and mirror Langmuir probe (MLP) data from the shot. Simulations differing in turbulence intensity were obtained by varying a dissipation parameter. Mean flow profiles and density fluctuation amplitudes are consistent with those measured by MLP in the experiment and with a Fourier space diagnostic designed to measure poloidal phase velocity. Blob velocities in the simulations were determined from the correlation function for density fluctuations, as in the analysis of gas-puff-imaging (GPI) blobs in the experiment. In the simulations, it was found that larger blobs moved poloidally with the ExB flow velocity, v E , in the near-SOL, while smaller fluctuations moved with the group velocity of the dominant linear (interchange) mode, v E + 1/2 v di , where v di is the ion diamagnetic drift velocity. Comparisons are made with the measured GPI correlation velocity for the discharge. The saturation mechanisms operative in the simulation of the discharge are also discussed. It is found that neither sheared flow nor pressure gradient modification can be excluded as saturation mechanisms. †email: dave@lodestar.com 2

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Section: Introductionmentioning

confidence: 99%

Mean flows and blob velocities in scrape-off layer (SOLT) simulations of an L-mode discharge on Alcator C-Mod

et al. 2016

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“…The transfer of energy between fluctuations and sheared flows has also been demonstrated by fluid simulations for interchange turbulence with cold ions [10][11][12]. Recently, the formation of transport barrier has been simulated with fluid models [17][18][19], in which the neoclassical terms are added in the vorticity equation with cold ions. In these simulations [17][18][19], the mean shear flows are generated mainly due to the neoclassical terms.…”

Section: Introductionmentioning

confidence: 99%

“…where represents the contribution of ion diamagnetic drift to the polarization current [3,4,[6][7][8], which is the crucial difference from the cold ion model [9][10][11][12][13][14][15][16][17][18][19]. The source terms S n and S E are added in Eqs.…”

Section: Model Equationsmentioning

confidence: 99%

“…Many of the conceptual points concerning turbulent energy transfer have been studied in both reduced models and in experimental investigations [19][20][21][22][23][24]. The transfer of energy between fluctuations and sheared flows has also been demonstrated by fluid simulations for interchange turbulence with cold ions [10][11][12].…”

Section: Introductionmentioning

confidence: 99%

“…Recently, the formation of transport barrier has been simulated with fluid models [17][18][19], in which the neoclassical terms are added in the vorticity equation with cold ions. In these simulations [17][18][19], the mean shear flows are generated mainly due to the neoclassical terms. In the present hot-ion model [3,4,[6][7][8],…”

Section: Introductionmentioning

confidence: 99%

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Fluctuation-induced shear flow and energy transfer in plasma interchange turbulence

Sun

Wang

et al. 2015

Physics of Plasmas

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Fluctuation-induced E × B shear flow and energy transfer for plasma interchange turbulence are examined in a flux-driven system with both closed and open magnetic field lines. The nonlinear evolution of interchange turbulence shows the presence of two confinement regimes characterized by low and high E × B flow shear. In the first regime, the large-scale turbulent convection is dominant and the mean E × B shear flow is at a relatively low level. By increasing the heat flux above a certain threshold, the increased turbulent intensity gives rise to the transfer of energy from fluctuations to mean E × B flows. As a result, a transition to the second regime occurs, in which a strong mean E × B shear flow is generated.

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The role of the thermal properties of electrons on the dispersion properties of Alfvén waves in space plasmas

Villarroel-Sepúlveda,

Moya,

López

et al. 2024

A&A

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The transition from left-hand to right-hand polarised Alfvén waves depends on the wavenumber, the ratio of kinetic to magnetic pressure, beta , the temperature anisotropy, and the ion composition of the plasma. Along with the temperature anisotropy, the electron-to-proton temperature ratio, $T_e/T_p$, is of great relevance for the characterisation of the thermal properties of a plasma. This ratio varies significantly between different space plasma environments. Thus, studying how variations in this ratio affect the polarisation properties of electromagnetic waves becomes highly relevant for our understanding of the dynamics of space plasmas. We present an extensive study on the effect of the thermal properties of electrons on the behaviour and characteristics of Alfvénic waves in fully kinetic linear theory, as well as on the transition from the electromagnetic ion-cyclotron wave to the kinetic Alfvén wave. We solved the fully kinetic dispersion relation for oblique electromagnetic waves of the Alfvén branch in a homogenous Maxwellian electron-proton plasma. We quantified the effect of the thermal properties of electrons by varying the electron-to-proton temperature ratio for different configurations of the propagation angle, $ nkT_p/B^2$, and wavenumber. We show that the temperature ratio, $T_e/T_p$, has strong and non-trivial effects on the polarisation of the Alfvénic modes, especially at kinetic scales ($k_ perp where perp =k theta is the propagation angle, and $ c_s/ with $c_s$ the plasma sound speed and $ the proton’s gyrofrequency) and $ We conclude that electron inertia plays an important role in the kinetic scale physics of the kinetic Alfvén wave in the warm plasma regime, and thus cannot be excluded in hybrid models for computer simulations.

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Flux-driven simulations of turbulence collapse

Cited by 33 publications

References 34 publications

Mean flows and blob velocities in scrape-off layer (SOLT) simulations of an L-mode discharge on Alcator C-Mod

Mean flows and blob velocities in scrape-off layer (SOLT) simulations of an L-mode discharge on Alcator C-Mod

Fluctuation-induced shear flow and energy transfer in plasma interchange turbulence

The role of the thermal properties of electrons on the dispersion properties of Alfvén waves in space plasmas

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