Drift waves and transport

TLDR

Drift waves are ubiquitous in magnetized plasmas and drive the primary transport of particles, energy, and momentum across magnetic field lines. The authors review laboratory experiments and theoretical models of drift‑wave turbulence, including density‑, temperature‑, and trapped‑particle‑driven instabilities, reduced‑fluid descriptions of mixed wave–vortex turbulence, weak turbulence theory, Kolmogorov spectra, mixing‑length approaches, and standard diffusivity formulas across space‑time scales. They show that sheared flows and magnetic shear can reduce Bohm‑level transport to the gyro‑Bohm rate, as demonstrated by large‑scale simulations.

Abstract

Drift waves occur universally in magnetized plasmas producing the dominant mechanism for the transport of particles, energy and momentum across magnetic field lines. A wealth of information obtained from quasistationary laboratory experiments for plasma confinement is reviewed for drift waves driven unstable by density gradients, temperature gradients and trapped particle effects. The modern understanding of Bohm transport and the role of sheared flows and magnetic shear in reducing the transport to the gyro-Bohm rate are explained and illustrated with large scale computer simulations. The types of mixed wave and vortex turbulence spontaneously generated in nonuniform plasmas are derived with reduced magnetized fluid descriptions. The types of theoretical descriptions reviewed include weak turbulence theory, Kolmogorov anisotropic spectral indices, and the mixing length. A number of standard turbulent diffusivity formulas are given for the various space-time scales of the drift-wave turbulent mixing.