Solitary zonal structures in subcritical drift waves: a minimum model

Zhou, Yao; Zhu, Hongxuan; Dodin, I. Y.

doi:10.1088/1361-6587/ab78f3

Cited by 9 publications

(11 citation statements)

References 45 publications

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“…These solutions might be related to those described by McMillan et al. (2009) and Zhou, Zhu & Dodin (2020). Models have been proposed for structure formation in a sheared flow that rely on the tilting of turbulence by shear and a nonzero group velocity to produce moving structures (McMillan et al.…”

Section: Nonlinear Saturation and Zonal Staircasesupporting

confidence: 78%

“…However, the quasi-linear system does have soliton solutions that are not localised poloidally, but rather appear to have a definite poloidal wavenumber k y . These solutions might be related to those described by McMillan et al (2009) and Zhou, Zhu & Dodin (2020). Models have been proposed for structure formation in a sheared flow that rely on the tilting of turbulence by shear and a nonzero group velocity to produce moving structures (McMillan et al 2018;Zhou et al 2020).…”

Section: Ferdinonsmentioning

confidence: 91%

“…These solutions might be related to those described by McMillan et al (2009) and Zhou, Zhu & Dodin (2020). Models have been proposed for structure formation in a sheared flow that rely on the tilting of turbulence by shear and a nonzero group velocity to produce moving structures (McMillan et al 2018;Zhou et al 2020). The radial group velocity is (at least in the Hasegawa-Mima-related models) proportional to the product k x k y , 9 which acquires a definite sign in the presence of flow shear ( § 4.3).…”

Section: Ferdinonsmentioning

confidence: 94%

“…2018; Zhou et al. 2020). The radial group velocity is (at least in the Hasegawa–Mima-related models) proportional to the product , 9 which acquires a definite sign in the presence of flow shear (§ 4.3).…”

Section: Nonlinear Saturation and Zonal Staircasementioning

confidence: 99%

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Zonally dominated dynamics and Dimits threshold in curvature-driven ITG turbulence

et al. 2020

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The saturated state of turbulence driven by the ion-temperature-gradient instability is investigated using a two-dimensional long-wavelength fluid model that describes the perturbed electrostatic potential and perturbed ion temperature in a magnetic field with constant curvature (a $Z$ -pinch) and an equilibrium temperature gradient. Numerical simulations reveal a well-defined transition between a finite-amplitude saturated state dominated by strong zonal-flow and zonal temperature perturbations, and a blow-up state that fails to saturate on a box-independent scale. We argue that this transition is equivalent to the Dimits transition from a low-transport to a high-transport state seen in gyrokinetic numerical simulations (Dimits et al., Phys. Plasmas, vol. 7, 2000, 969). A quasi-static staircase-like structure of the temperature gradient intertwined with zonal flows, which have patch-wise constant shear, emerges near the Dimits threshold. The turbulent heat flux in the low-collisionality near-marginal state is dominated by turbulent bursts, triggered by coherent long-lived structures closely resembling those found in gyrokinetic simulations with imposed equilibrium flow shear (van Wyk et al., J. Plasma Phys., vol. 82, 2016, 905820609). The breakup of the low-transport Dimits regime is linked to a competition between the two different sources of poloidal momentum in the system – the Reynolds stress and the advection of the diamagnetic flow by the $\boldsymbol {E}\times \boldsymbol {B}$ flow. By analysing the linear ion-temperature-gradient modes, we obtain a semi-analytic model for the Dimits threshold at large collisionality.

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Section: Nonlinear Saturation and Zonal Staircasesupporting

confidence: 78%

Section: Ferdinonsmentioning

confidence: 91%

Section: Ferdinonsmentioning

confidence: 94%

Section: Nonlinear Saturation and Zonal Staircasementioning

confidence: 99%

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Zonally dominated dynamics and Dimits threshold in curvature-driven ITG turbulence

et al. 2020

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“…Although reduced fluid models can rarely be derived self-consistently from first principles for the values of the plasma parameters measured in magnetic confinement fusion experiments, they have been useful to identify the elementary building blocks required for the emergence of zonal flows from drift wave turbulence [6,26,21,33], the associated reduction of turbulence driven transport [36,42,20], as well as the nonlocal transport characterized by ballistic bursts called avalanches [35,4] and long-time-coherent, soliton-like traveling structures, for which the term "ferdinons" was recently coined [41,20]. In this article, we demonstrate that our recently proposed flux-balanced Hasegawa-Wakatani (BHW) model [21,33] is one of the simplest models which captures all of these characteristic features of turbulent transport in magnetic confinement fusion devices.…”

Section: Introductionmentioning

confidence: 99%

Dimits shift, avalanche-like bursts, and Solitary propagating structures in the two-field Flux-Balanced Hasegawa-Wakatani model for plasma edge turbulence

Qi,

Majda,

Cerfon

2020

Preprint

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We show that the recently introduced two-field flux-balanced Hasegawa-Wakatani (BHW) model captures the key features of drift-wave turbulent transport mediated by zonal flows observed in more complete and accurate gyrokinetic simulations, such as the existence of a nonlinear upshift of the treshold for drift wave turbulence driven transport, often called the Dimits shift, as well as non-local transport with avalanche bursts and solitary propagating structures. Because of the approximations made in the BHW model, these observations are made for the particle flux instead of the heat flux more commonly studied in ion temperature gradient (ITG) driven turbulence in fluid or gyrokinetic codes. Many of these features are not seen in other Hasegawa-Wakatani models, which confirms the critical role of the electron dynamics parallel to the magnetic field lines. To address questions regarding the role of boundary conditions on the drift-wave zonal flow dynamics, we apply our model to both a channel domain geometry and the more typical doubly periodic geometry. We only observe strong soliton-like solutions in the particle flux for the channel geometry, in the vicinity of the boundaries, where strong velocity shear and density gradients are generated which are absent in the doubly periodic simulations. Changing the aspect ratio of the simulation domain also has a significant effect. In domains which are elongated in the radial direction, more complex multiscale dynamics takes place, with multiple zonal jets interacting with each other, and large scale avalanches.

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Dimits shift, avalanche-like bursts, and solitary propagating structures in the two-field flux-balanced Hasegawa–Wakatani model for plasma edge turbulence

Majda

Cerfon

2020

Physics of Plasmas

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We show that the recently introduced two-field flux-balanced Hasegawa–Wakatani (BHW) model captures the key features of drift-wave turbulent transport mediated by zonal flows observed in more complete and accurate gyrokinetic simulations, such as the existence of a nonlinear upshift of the threshold for drift wave turbulence driven transport, often called the Dimits shift, as well as non-local transport with avalanche bursts and solitary propagating structures. Because of the approximations made in the BHW model, these observations are made for the particle flux instead of the heat flux more commonly studied in ion temperature gradient (ITG) driven turbulence in fluid or gyrokinetic codes. Many of these features are not seen in other Hasegawa–Wakatani models, which confirm the critical role of the electron dynamics parallel to the magnetic field lines. To address questions regarding the role of boundary conditions on the drift-wave zonal flow dynamics, we apply our model to both a channel domain geometry and the more typical doubly periodic geometry. We only observe strong soliton-like solutions in the particle flux for the channel geometry, in the vicinity of the boundaries, where strong velocity shear and density gradients are generated, which are absent in the doubly periodic simulations. Changing the aspect ratio of the simulation domain also has a significant effect. In domains which are elongated in the radial direction, more complex multi-scale dynamics takes place, with multiple zonal jets interacting with each other, and large scale avalanches.

show abstract

Solitary zonal structures in subcritical drift waves: a minimum model

Cited by 9 publications

References 45 publications

Zonally dominated dynamics and Dimits threshold in curvature-driven ITG turbulence

Zonally dominated dynamics and Dimits threshold in curvature-driven ITG turbulence

Dimits shift, avalanche-like bursts, and Solitary propagating structures in the two-field Flux-Balanced Hasegawa-Wakatani model for plasma edge turbulence

Dimits shift, avalanche-like bursts, and solitary propagating structures in the two-field flux-balanced Hasegawa–Wakatani model for plasma edge turbulence

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