Drift wave propagation as a source of plasma edge turbulence: Toroidal theory

Recently [N. Mattor and P. H. Diamond, Phys. Rev. Lett. 72, 486 (1994)] it was suggested that large-amplitude turbulence in edge plasmas [ñ/n0∼O(1)] could originate from the core, propagating outward into the regions of low density and temperature. Here this theory is expanded, using a toroidal geometry. It is shown that a wave launched in the core region can propagate over a substantial portion of the radius, reaching the edge from the core. It is shown that a large increase of plasma flow from core to edge causes wave reflection, cutting off the source of edge turbulence. Experimental evidence is discussed, with particular attention to subtleties of global mode structure in a torus. Possible new experimental tests of this theory are discussed. Details are given of a new theory to explain the observed correlation between edge shear flows and improved confinement (‘‘H’’ modes), which are compared to experiment.