Decay instability of a lower hybrid wave

A study is made of the decay instability of a lower hybrid wave with a finite wave vector (k ₀≠0) and a large amplitude such that the oscillatory velocity of the electrons with respect to the ions cannot be neglected. It is shown that, depending on the angle between the propagation direction of the lower hybrid wave and the external magnetic field and the angle through which the wave is scattered, the decay instability is primarily governed either by the oscillatory electron motion with respect to the ions or by the nonlinear response of the plasma to the lower hybrid wave propagating in it. The role of the nonlinear frequency shift in the saturation of the lower hybrid decay instability is clarified.