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

Abstract

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.

Non-local transport nature revealed by the research in transient phenomena of toroidal plasma

“…The inhomogeneous mixing produces corrugations and E × B shear layer. This process is a mechanism for zonal profile corrugations and staircase formation (Leconte and Kobayashi 2021). These corrugations contribute to the formation of local barriers and drive avalanches or turbulence pulses, as seen in Fig.…”

Joint meeting of 9th Asia Pacific-Transport Working Group (APTWG) & EU-US Transport Task Force (TTF) workshop

“…Leconte proposed a new physical mechanism to generate profile corrugations in drift-wave turbulence. He presented a 1D reduced model, namely an extended wave-kinetic model [40], derived from the 2D modified Hasegawa-Wakatani model. Focusing on the role of the cross-phase between density and potential fluctuation in suppressing turbulent transport, a novel route for the formation of zonal structures was investigated.…”

Limit Cycle Oscillations, response time and the time-dependent solution to the Lotka-Volterra Predator-Prey model

“…In applications to plasma turbulence, the predator is usually taken as zonal flow energy, and the prey as turbulence energy [6,7,8]. Here, we take the predator as zonal density corrugations driven by nonlinear modulation of the transport crossphase [16] and the prey as turbulence energy. In section 3, this model will be applied to gyrokinetic simulations of CTEM turbulence.…”

“…In the simplified framework of Drift-wave turbulence, there are several candidates to explain the interaction between zonal density corrugations and the turbulence. One of the author (M. Leconte) proposed a model based on the nonlinear modulation of the transport crossphase between density and potential perturbations [16,17]. Another model, based on stochastic noise due to turbulence was proposed in Ref.…”