Excitation of zonal flows by kinetic Alfven waves

Nonlinear couplings between dispersive kinetic Alfven waves (DKAWs) and electrostatic convective cells/zonal flows are reexamined. A set of equations that exhibit nonlinear couplings between the scalar and parallel vector potentials of the DKAWs and the scalar potential of zonal flows that are reinforced by the Reynolds stresses of the DKAWs in a magnetized plasma is presented. The equations are then Fourier-analyzed to obtain the nonlinear dispersion relation. The latter exhibits modulational instabilities, which could be responsible for enhanced zonal flows in a uniform magnetized plasma. Zonal flows can regulate the transport of plasma particles in laboratory magnetoplasmas as well as in the Earth's magnetosphere and in the solar corona