English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

A new basis has been found for the theory of self-organization of transportavalanches and jet zonal flows in L-mode tokamak plasma, the so-called "plasmastaircase." The jet zonal flows are considered as a wave packet of couplednonlinear oscillators characterized by a complex time- and wave-numberdependent wave function; in a mean-field approximation this function is arguedto obey a discrete nonlinear Schr\"odinger equation with subquadratic powernonlinearity. It is shown that the subquadratic power leads directly to a whiteL\'evy noise, and to a L\'evy-fractional Fokker-Planck equation for radialtransport of test particles (via wave-particle interactions). In aself-consistent description the avalanches, which are driven by the whiteL\'evy noise, interact with the jet zonal flows, which form a system ofsemi-permeable barriers to radial transport. We argue that the plasma staircasesaturates at a state of marginal stability, in whose vicinity the avalanchesundergo an ever-pursuing localization-delocalization transition. At thetransition point, the event-size distribution of the avalanches is found to bea power-law $w_\tau (\Delta n) \sim \Delta n^{-\tau}$, with the drop-offexponent $\tau = ({\sqrt{17}} + 1)/{2} \simeq 2.56$. This value is an exactresult of the self-consistent model. The edge behavior bears signaturesenabling to associate it with the dynamics of a self-organized critical (SOC)state. At the same time the critical exponents, pertaining to this state, arefound to be inconsistent with classic models of avalanche transport based onsand-piles and their generalizations, suggesting that the coupled avalanche-jetzonal flow system operates on different organizing principles. The resultsobtained have been validated in a numerical simulation of the plasma staircaseusing flux-driven gyrokinetic code for L-mode Tore-Supra plasma.

A self-consistent model of the plasma staircase and nonlinear Schr\"odinger equation with subquadratic power nonlinearity