Non-linear features of the electron temperature gradient mode and electron thermal transport in tokamaks

Abstract

Analytical investigations of several linear and non-linear features of ETG turbulence are reported. The linear theory includes effects such as finite beta induced electromagnetic shielding and coupling to electron magnetohydrodynamic modes such as whistlers. It is argued that non-linearity, turbulence and transport are dominated by radially extended modes called 'streamers'. A non-linear mechanism generating streamers based on a modulational instability theory of the ETG turbulence is also presented. The saturation levels of the streamers using a Kelvin-Helmholtz secondary instability mechanism are calculated and levels of the electron thermal transport due to streamers are estimated.