Zonal flow excitation in plasmas by electron-temperature-gradient modes

The nonlinear coupling between short-wavelength electron-temperature-gradient (ETG) modes and zonal flows in plasmas is considered. The mode-coupling equations are derived by using a Boltzmann ion distribution and a fluid electron response described by the hydrodynamic and energy equations. A dispersion relation for the nonlinearly coupled ETG modes and the zonal flows is derived. The results show enhanced zonal flows, which can affect the electron energy transport in tokamaks and stellarators.