Global E × B flow pattern formation and saturation

Qi, Lei; Choi, M.; Leconte, M.; Hahm, Tae Soo; Kwon, Jae-Min

doi:10.1088/1741-4326/ac906f

Cited by 7 publications

(3 citation statements)

References 38 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…[21] is valid only for the initial exponential growth of the modulational instability. The fluid model (1,2) could possibly be extended to CTEM, where zonal density generation seems to play a crucial role [40,41]. Another point is about the importance of density nonlinear structures.…”

Section: Discussionmentioning

confidence: 99%

Zonal profile corrugations and staircase formation: Role of the transport crossphase

Leconte

Kobayashi

2021

Physics of Plasmas

View full text Add to dashboard Cite

Recently, quasi-stationary structures called E × B staircases were observed in gyrokinetic simulations, in all transport channels [Dif-Pradalier et al. Phys. Rev. Lett. 114, 085004 (2015)]. We present a novel analytical theory -supported by collisional drift-wave fluid simulations -for the generation of density profile corrugations (staircase), independent of the action of zonal flows: Turbulent fluctuations self-organize to generate quasistationary radial modulations ∆θ k (r, t) of the transport crossphase θ k between density and electric potential fluctuations. The radial modulations of the associated particle flux drive zonal corrugations of the density profile, via a modulational instability. In turn, zonal density corrugations regulate the turbulence via nonlinear damping of the fluctuations.

show abstract

Section: Discussionmentioning

confidence: 99%

Zonal profile corrugations and staircase formation: Role of the transport crossphase

Leconte

Kobayashi

2021

Physics of Plasmas

View full text Add to dashboard Cite

show abstract

“…With the time delay between variations of a field and its flux, the avalanche flux propagation can be jammed to form a seed perturbation (temperature corrugation) of the transport barrier [36]. Note that recent gyrokinetic simulations found that there exists such a time delay in both temperature [60] and density [61]. The jamming occurs when an avalanche is so fast to overtake a wave that can be carried by the system.…”

Section: The E × B Staircase and Its Avalanche Stopping Capabilitymentioning

confidence: 99%

Mesoscopic transport in KSTAR plasmas: avalanches and the E × B staircase

Choi,

Kwon,

et al. 2024

Plasma Phys. Control. Fusion

Self Cite

View full text Add to dashboard Cite

The self-organization is one of the most interesting phenomena in the non-equilibrium complex system, generating ordered structures of different sizes and durations. In tokamak plasmas, various self-organized phenomena have been reported, and two of them, coexisting in the near-marginal (interaction dominant) regime, are avalanches and the E × B staircase. Avalanches mean the ballistic flux propagation event through successive interactions as it propagates, and the E × B staircase means a globally ordered pattern of self-organized zonal flow layers. Various models have been suggested to understand their characteristics and relation, but experimental researches have been mostly limited to the demonstration of their existence. Here we report detailed analyses of their dynamics and statistics and explain their relation. Avalanches influence the formation and the width distribution of the E × B staircase, while the E × B staircase confines avalanches within its mesoscopic width until dissipated or penetrated. Our perspective to consider them the self-organization phenomena enhances our fundamental understanding of them as well as links our findings with the self-organization of mesoscopic structures in various complex systems.

show abstract

“…[15][16][17][18]. The other approach is the jams model [19][20][21]. In this alternative picture, the staircase forms due to a time delay between temperature modulations and local heat flux.…”

Section: A Backgroundmentioning

confidence: 99%

Staircase resiliency in a fluctuating cellular array

Ramirez,

Diamond

2024

Phys. Rev. E

View full text Add to dashboard Cite

Inhomogeneous mixing by stationary convective cells set in a fixed array is a particularly simple route to layering. Layered profile structures, or staircases, have been observed in many systems, including drift-wave turbulence in magnetic confinement devices. The simplest type of staircase occurs in passive-scalar advection, due to the existence and interplay of two disparate timescales, the cell turn-over (τ H ), and the cell diffusion (τ D ) time. In this simple system, we study the resiliency of the staircase structure in the presence of global transverse shear and weak vortex scattering. The fixed cellular array is then generalized to a fluctuating vortex array in a series of numerical experiments. The focus is on regimes of low-modest effective Reynolds numbers, as found in magnetic fusion devices. By systematically perturbing the elements of the vortex array, we learn that staircases form and are resilient (although steps become less regular, due to cell mergers) over a broad range of Reynolds numbers. The criteria for resiliency are (a) τ D τ H and (b) a sufficiently high profile curvature (κ 1.5). We learn that scalar concentration travels along regions of shear, thus staircase barriers form first, and scalar concentration "homogenizes" in vortices later. The scattering of vortices induces a lower effective speed of scalar concentration front propagation. The paths are those of the least time. We observe that if background diffusion is kept fixed, the cell geometric properties can be used to derive an approximation for the effective diffusivity of the scalar. The effective diffusivity of the fluctuating vortex array does not deviate significantly from that of the fixed cellular array.

show abstract

Global E × B flow pattern formation and saturation

Cited by 7 publications

References 38 publications

Zonal profile corrugations and staircase formation: Role of the transport crossphase

Zonal profile corrugations and staircase formation: Role of the transport crossphase

Mesoscopic transport in KSTAR plasmas: avalanches and the E × B staircase

Staircase resiliency in a fluctuating cellular array

Contact Info

Product

Resources

About