Parametric excitation of a kinetic Alfven wave at the ion-cyclotron frequency

The parametric decay of an electrostatic ion-cyclotron wave into a low-frequency mixed-mode (EM-ES) kinetic Alven wave and an electrostatic ion-cyclotron side-band has been investigated in a homogeneous low-β plasma. A nonlinear dispersion relation describing this parametric interaction is derived. The partially electrostatic nature of the kinetic Alfven wave and the component of the low-frequency ponderomotive force along the direction of the external magnetic field lead to the dominant coupling. Possible applications in the ionosphere, in the earth's magnetosphere and in laboratory plasmas are discussed. (author)