PONDEROMOTIVE INTERACTION OF ELECTROSTATIC AND ELECTROMAGNETIC PARAMETRIC-INSTABILITIES IN ACTIVE EXPERIMENTS IN-SPACE

We show that the ponderomotive coupling of electrostatic Langmuir parametric instabilities and electromagnetic filamentation instability can occur in the vicinity of the reflection level where the frequency of the high power heater radio wave, injected into space plasmas by active experiments, is near the local plasma frequency. In general, the heater-generated parametric instabilities are not purely electrostatic or electromagnetic in the proximity of the critical density, but become hybrid (coupled electrostatic-electromagnetic) modes. As a result, the growth rate and bandwidth of the parametric decay line are significantly modified by the electromagnetic effects.