Saturation of magnetised plasma turbulence by propagating zonal flows
Abstract
Strongly driven ion-scale turbulence in tokamak plasmas is shown to be regulated by a new propagating zonal flow mode, the toroidal secondary mode, which is nonlinearly supported by the turbulence. The mode grows and propagates due to the combined effects of zonal flow shearing and advection by the magnetic drift. Above a threshold in the turbulence level, small-scale toroidal secondary modes become unstable and shear apart turbulent eddies, forcing the turbulence level to remain near the threshold. This threshold condition is used to derive scaling laws for the turbulent heat flux, fluctuation spectra, and zonal flow amplitude, which are validated in nonlinear gyrokinetic simulations and explain previous experimental observations.
Keywords
Cite
@article{arxiv.2409.02283,
title = {Saturation of magnetised plasma turbulence by propagating zonal flows},
author = {Richard Nies and Felix Parra and Michael Barnes and Noah Mandell and William Dorland},
journal= {arXiv preprint arXiv:2409.02283},
year = {2026}
}
Comments
New version with major revisions. Accepted in Physical Review Research. 9 pages, 9 figures