The role of magnetic shear for zonal flow generation

Artikel i vetenskaplig tidskrift, 2006

The role of magnetic shear for zonal flow generation by ion temperature gradient and trapped electron (TE) mode turbulence is studied analytically using fluid descriptions. The scaling of the zonal flow (ZF) growth rate with magnetic shear is examined and compared with linear growth rates for typical tokamak parameter values. The results indicate that large levels of ZF are obtained in regions of negative magnetic shear, especially for ZF driven by TE mode turbulence. The strong magnetic shear scaling obtained for TE-mode-driven ZFs originates from the bounce average of the electron magnetic drifts.