PARAMETRIC DECAY OF UPPER HYBRID PLASMA-WAVES TRAPPED INSIDE DENSITY IRREGULARITIES IN THE IONOSPHERE

The parametric decay of an upper hybrid (UH) wave into a lower hybrid (LH) wave and a downshifted UH wave inside inhomogeneous ionospheric s triations, when both pump and decay UH modes are trapped, is investiga ted. The threshold and the growth rate of the instability are determin ed. The possibility of the existence of both main features in the usua lly observed spectrum of stimulated electromagnetic emission (SEE), do wnshifted maximum and long continuum tail, is demonstrated. The condit ions of the excitation of the second and third decay modes are establi shed. (C) 1997 Published by Elsevier Science B.V.