In toroidally confined fusion plasma experiments the term zonal flow means a plasma flow within a magnetic surface primarily in the poloidal direction. This usage is inspired by the analogy between the quasi-two-dimensional nature of large-scale atmospheric and oceanic flows, where zonal means latitudinal, and the similarly quasi-two-dimensional nature of low-frequency flows in a strongly magnetized plasma.

Zonal flows in the toroidal plasma context are further characterized by

  • being localized in their radial extent transverse to the magnetic surfaces (in contrast to global plasma rotation),
  • having little or no variation in either the poloidal or toroidal direction—they are m = n = 0 modes (where m and n are the poloidal and toroidal mode numbers, respectively),
  • having zero real frequency when analyzed by linearization around an unperturbed toroidal equilibrium state (in contrast to the geodesic acoustic mode branch, which has finite frequency).
  • Arising via a self-organization phenomenon driven by low-frequency drift-type modes, in which energy is transferred to longer wavelengths by modulational instability or turbulent inverse cascade.

See also

  • Diamond, P. H.; Itoh, S.-I.; Itoh, K.; Hahm, T.S. (2005). (PDF). Plasma Phys. Control. Fusion. 47 (5): R35–R161. Bibcode:. doi:. S2CID .
  • Dewar, R. L.; Abdullatif, R. F. (2007). . In Denier, J. P.; Frederiksen, J. S. (eds.). Frontiers in Turbulence and Coherent Structures - World Scientific Lecture Notes in Complex Systems. . Vol. 6. Singapore: World Scientific. pp. 415–430. arXiv:. Bibcode:. doi:. ISBN 978-981-270-393-4. Archived from on 24 January 2008.