Zonal flows in plasma—a review

TLDR

Zonal flows are examined in laboratory plasmas, with planetary zonal flows also discussed. This review surveys zonal flow phenomena in plasmas, compares experiment with theory, and outlines future research directions. It synthesizes theory, numerical simulations, and experiments to build an integrated understanding of drift‑wave–zonal‑flow turbulence, including generation, back‑interaction, and regulatory feedback loops. The review discusses how zonal flows affect confinement and other phenomena in fusion devices.

Abstract

A comprehensive review of zonal flow phenomena in plasmas is presented. While the emphasis is on zonal flows in laboratory plasmas, planetary zonal flows are discussed as well. The review presents the status of theory, numerical simulation and experiments relevant to zonal flows. The emphasis is on developing an integrated understanding of the dynamics of drift wave–zonal flow turbulence by combining detailed studies of the generation of zonal flows by drift waves, the back-interaction of zonal flows on the drift waves, and the various feedback loops by which the system regulates and organizes itself. The implications of zonal flow phenomena for confinement in, and the phenomena of fusion devices are discussed. Special attention is given to the comparison of experiment with theory and to identifying directions for progress in future research.