SIMULATION STUDIES OF PARAMETRIC DECAY PROCESSES ASSOCIATED WITH IONOSPHERIC STIMULATED RADIATION

Parametric instability processes are thought to produce stimulated ele ctromagnetic emissions during ionospheric heating experiments. The phe nomenon is primarily attributed to plasma turbulence excited by the hi gh-frequency heater in the altitude region where the pump frequency om ega(0) is near the plasma upper hybrid frequency omega(uh). In this st udy, parametric instability processes thought to produce ionospheric s timulated radiation are studied using electrostatic particle-in-cell s imulation models. The emphasis in this work will be to consider the ex citation and interactions between electrostatic waves generated by the pump wave. The simulation plasma is driven with a uniform oscillating electric field directed nearly perpendicular to the background geomag netic field B to consider interactions when omega(uh) is near electron cyclotron harmonics n Omega(ce). The pump frequency and amplitude are varied to consider the effects on the simulation electric field power spectrum. Also, the effect of varying the electron to ion temperature ratio T-e/T-i is discussed and evaluated. The simulation results show richly structured sidebands upshifted and downshifted above and below the pump frequency, which are attributed to parametric instability pr ocesses. The relationship between the simulation results, the theoreti cal models, and the experimental spectrum are discussed.