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Saturation of magnetized plasma turbulence by propagating zonal flows

R. Nies1,2,*, F. Parra1,2, M. Barnes3, N. Mandell2, and W. Dorland4,†

  • *Contact author: richard.nies@physics.ox.ac.uk
  • †Deceased.
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Phys. Rev. Research 8, 013295 – Published 17 March, 2026

DOI: https://doi.org/10.1103/yf4h-4hvw

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.

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Phys. Rev. Research 8, 013295– Published 17 March, 2026
  • Received 9 September 2024
  • Accepted 11 February 2026
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Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.

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