The Plasma E × B Staircase: Turbulence Self-Regulation through Spontaneous Flow Patterning

Abstract : The E × B staircase [1, 2] is a spontaneously formed, turbulence-driven self-organising pattern of quasi-regular, long-lived and localised shear flow [3] and stress layers. These layers coincide with long-lived pressure corrugations and are interspersed between regions of turbulent avalanching. The typical spacing between these layers is mesoscale, noted ∆ ∼ 25 − 30ρ i [1, 4] —in-between the turbulence auto-correlation length c ∼ 5ρ i at micro scales and the profile macroscale L 100ρ i , see e.g. Fig.2 in [1]— and sets the outer scale of the turbulent avalanching. Here ρ i is ion Larmor radius. Whilst arresting, statistically, to mesoscales the detrimental avalanching these layers, located at the " steps of the staircase " are beneficial to confinement. The E×B staircase is thus best understood as a self-organising and dynamical set of weak or permeable transport barriers. Strong mean zonal flows are generated and endure at the steps of the staircase, resulting in localised deviations of the poloidal flow from its oft-assumed neoclassical prediction [5].
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Guilhem Dif-Pradalier, G Hornung, Philippe Ghendrih, R Clairet, P Diamond, et al.. The Plasma E × B Staircase: Turbulence Self-Regulation through Spontaneous Flow Patterning. 42nd European Physical Society Conference on Plasma Physics, Lisbon, Portugal, France. 2015. ⟨cea-01468381⟩

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