Influence of zonal flow and density on resistive drift wave turbulent transport

Zhang, Yanzeng; Krasheninnikov, S. I.

doi:10.1063/5.0025861

Cited by 11 publications

(13 citation statements)

References 30 publications

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“…It was recently conjectured by Zhang & Krasheninnikov (2020) that localising well-defined staircases like these may provide effective transport barriers of drift waves and drifting coherent structures like ferdinons (Ivanov et al 2020), reflecting and trapping As can be seen, the ion temperature (blue) and the electron temperature (red, dotted) tend to display opposite signs over a majority of the region. Meanwhile, it can be seen that as the gradient is increased towards the Dimits threshold the stable zonal flow by necessity increasingly resembles a staircase state with broadening 'steps' of nearly constant zonal shear ∂ 2 x φ.…”

Section: Localisationmentioning

confidence: 96%

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Predicting the Z-pinch Dimits shift through gyrokinetic tertiary instability analysis of the entropy mode

Hallenbert

Plunk

2022

J. Plasma Phys.

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The Dimits shift, an upshift in the onset of turbulence from the linear instability threshold, caused by self-generated zonal flows, can greatly enhance the performance of magnetic confinement plasma devices. Except in simple cases, using fluid approximations and model magnetic geometries, this phenomenon has proved difficult to understand and quantitatively predict. To bridge the large gap in complexity between simple models and realistic treatment in toroidal magnetic geometries (e.g. tokamaks or stellarators), the present work uses fully gyrokinetic simulations in a Z-pinch geometry to investigate the Dimits shift through the lens of tertiary instability analysis, which describes the emergence of drift waves from a zonally dominated state. Several features of the tertiary instability, previously observed in fluid models, are confirmed to remain. Most significantly, an efficient reduced-mode tertiary model, which previously proved successful in predicting the Dimits shift in a gyrofluid limit (Hallenbert & Plunk, J. Plasma Phys., vol. 87, issue 05, 2021, 905870508), is found to be accurate here, with only slight modifications to account for kinetic effects.

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Section: Localisationmentioning

confidence: 96%

Section: Nonlinear Simulationsmentioning

confidence: 99%

Predicting the Z-pinch Dimits shift through gyrokinetic tertiary instability analysis of the entropy mode

Hallenbert

Plunk

2022

J. Plasma Phys.

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“…and Ω ± k is given in (10). Note that these coefficients are complex, and have different phases in general.…”

Section: Nonlinear Termsmentioning

confidence: 99%

“…Hasegawa-Mima model does not [5]), ii) finite frequency (so that resonant interactions are possible [6]), and iii) a proper treatment of zonal flows [7]. The model is well known to generate high levels of large scale zonal flows, especially for C 1 [8][9][10]. It has been studied in detail for many problems in fusion plasmas including dissipative drift waves in tokamak edge [11,12], subcritical turbulence [13], trapped ion modes [14], intermittency [15,16], closures [17][18][19], feedback control [20], information geometry [21] and machine learning [22].…”

Section: Introductionmentioning

confidence: 99%

Phase and amplitude evolution in the network of triadic interactions of the Hasegawa-Wakatani system

Gürcan¹,

Anderson²,

Moradi³

et al. 2022

Preprint

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Hasegawa-Wakatani system, commonly used as a toy model of dissipative drift waves in fusion devices is revisited with considerations of phase and amplitude dynamics of its triadic interactions. It is observed that a single resonant triad can saturate via three way phase locking where the phase differences between dominant modes converge to constant values as individual phases increase in time. This allows the system to have approximately constant amplitude solutions. Non-resonant triads show similar behavior only when one of its legs is a zonal wave number. However when an additional triad, which is a reflection of the original one with respect to the y axis is included, the behavior of the resulting triad pair is shown to be more complex. In particular, it is found that triads involving small radial wave numbers (large scale zonal flows) end up transferring their energy to the subdominant mode which keeps growing exponentially, while those involving larger radial wave numbers (small scale zonal flows) tend to find steady chaotic or limit cycle states (or decay to zero). In order to study the dynamics in a connected network of triads, a network formulation is considered including a pump mode, and a number of zonal and non-zonal subdominant modes as a dynamical system. It was observed that the zonal modes become clearly dominant only when a large number of triads are connected. When the zonal flow becomes dominant as a 'collective mean field', individual interactions between modes become less important, which is consistent with the inhomogeneous wave-kinetic picture. Finally, the results of direct numerical simulation is discussed for the same parameters and various forms of the order parameter are computed. It is observed that nonlinear phase dynamics results in a flattening of the large scale phase velocity as a function of scale in direct numerical simulations.

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“…For example, if n e and ϕ are connected via Ohm's law, one is led to a set of two-field equations known as the modified Hasegawa-Wakatani equation. [45][46][47][48][49] This model can be applied to resistive DWs at the tokamak edge. Similar two-field models have also been proposed for core plasmas, including ones that describe the ion-temperature-gradient (ITG) mode, 8,38,50,51 trapped-electron modes, 52 etc.…”

Section: Basic Equationsmentioning

confidence: 99%

Wave-kinetic approach to zonal-flow dynamics: recent advances

Zhu,

Dodin

2021

Preprint

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Basic physics of drift-wave turbulence and zonal flows has long been studied within the framework of wavekinetic theory. Recently, this framework has been re-examined from first principles, which has led to more accurate yet still tractable "improved" wave-kinetic equations. In particular, these equations reveal an important effect of the zonal-flow "curvature" (the second radial derivative of the flow velocity) on dynamics and stability of drift waves and zonal flows. We overview these recent findings and present a consolidated high-level picture of (mostly quasilinear) zonal-flow physics within reduced models of drift-wave turbulence.

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Influence of zonal flow and density on resistive drift wave turbulent transport

Cited by 11 publications

References 30 publications

Predicting the Z-pinch Dimits shift through gyrokinetic tertiary instability analysis of the entropy mode

Predicting the Z-pinch Dimits shift through gyrokinetic tertiary instability analysis of the entropy mode

Phase and amplitude evolution in the network of triadic interactions of the Hasegawa-Wakatani system

Wave-kinetic approach to zonal-flow dynamics: recent advances

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