Parametric decay instabilities of the fast wave in the lower hybrid frequency regime

Three possible delay instabilities of the fast wave in the lower hybrid frequency regime are presented. It has been considered that a fast wave may decay into a high-frequency, lower hybrid wave and a low-frequency wave, either the ion-Bernstein wave, ion-acoustic wave, or kinetic Alfven wave. Explicit expressions for growth rates, homogeneous thresholds, and convective thresholds have been given. Applications have been pointed out in tokamak plasma during current drive experiments and magnetospheric plasmas. For example, for PLT tokamak parameters, the convective threshold for the decay instability of the fast wave into lower hybrid and ion acoustic wave is approximately 180 W/cm/sup 2/.<>