Alfvén wave phase mixing driven by velocity shear in two-dimensional open magnetic configurations

Abstract

Phase mixing of torsional Alfvén waves in axisymmetric equilibrium magnetic configurations with purely poloidal magnetic field and stationary flow along the field lines in resistive viscous plasmas is studied. The characteristic wavelength along the magnetic field lines is assumed to be much smaller than the characteristic scale of inhomogeneity in the magnetic field direction, and the WKB method is used to obtain an analytic solution describing phase mixing. The general solution is applied to a particular configuration with the radial magnetic field and flow under the assumptions that the magnetic field and density are independent of the polar angle in the spherical coordinates and the flow velocity is independent of the radial coordinate. The only source of phase mixing in this configuration is velocity shear. The analytical solution is compared with a numerical simulation of the fully nonlinear resistive MHD equations. The numerical and analytical results are in good agreement. Consequences for wave energy deposition into the solar corona and solar wind and for the evolution of the Alfvén wave energy spectrum are discussed.