An extended K-dV equation for nonlinear magnetosonic wave in a multi-ion plasma

Nonlinear magnetosonic waves propagating perpendicularly to a magnetic field are studied in two-ion plasma. It is shown that a high frequency magnetosonic wave under the influence of finite cut-off frequency can be described by an extended K-dV equation, rather than a conventional K-dV equation. The modulational stability of this mode is strongly affected by the finite cut-off frequency in two-ion plasma.