Enhancement of zonal flow damping due to resonant magnetic perturbations in the background of an equilibrium $E \times B$ sheared flow

TL;DR

This paper demonstrates that equilibrium sheared flows can significantly enhance the damping of zonal flows caused by resonant magnetic perturbations, with the effect depending on magnetic shear and perturbation amplitude.

Contribution

It introduces a parametric interaction formalism showing how sheared flows amplify zonal flow damping due to magnetic perturbations, extending previous understanding.

Findings

Damping effect is proportional to (L_s/L_V)^2 and δB_r^2/B^2.

Sheared flow increases the damping of zonal flows.

External magnetic perturbations combined with shear significantly influence plasma stability.

Abstract

Using a parametric interaction formalism, we show that the equilibrium sheared rotation can enhance the zonal flow damping effect found in Ref. [M. Leconte and P.H. Diamond, \emph{Phys. Plasmas} 19, 055903 (2012)]. This additional damping contribution is proportional to $(L_s/L_V)^2 \times \delta B_r^2 / B^2$, where $L_s/L_V$ is the ratio of magnetic shear length to the scale-length of equilibrium $E \times B$ flow shear, and $\delta B_r / B$ is the amplitude of the external magnetic perturbation normalized to the background magnetic field.