It is shown that an electrostatic wave near the upper‐hybrid resonance frequency can parametrically excite extraordinary (X‐) mode radiation accompanied by a great variety of low‐frequency oscillations. The latter may include the lower‐hybrid, the electron‐acoustic, the ion‐cyclotron, and the shear Alfve´n waves. Nonlinear dispersion relations and the growth rates are obtained for each case. Comparison of our investigation to an earlier work and its possible application to space plasmas are pointed out.