On the excitation of zonal flows by wave particle resonances

Excitation of zonal flows by ion temperature gradient driven modes have been studi using both fluid and kinetic models. Previous fluid derivations have shown that a strong excitation of zonal flows occurs through the nonlinearity in the energy equation and is enhanced by the fluid magnetic drift resonance. Thus a new derivation has been made by nonlinear kinetic theory, confirming that a strong excitation occurs through the kinetic magnetic drift resonance. A new fluid derivation is also presented. Fluid and kinetic results are compared. (author)