LABORATORY REPRODUCTION OF ARECIBO EXPERIMENTAL RESULTS - HF WAVE-ENHANCED LANGMUIR-WAVES

Laboratory experiments at ha using the Versatile Toroidal Facility (VT F) have produced ''cascading'' and ''frequency-upshifted'' spectra of HF wave-enhanced Langmuir waves resembling the spectra observed in Are cibo experiments. The VTF experiments are well-explained using the sou rce mechanism proposed by Kuo and Lee [1992] to interpret observed Lan gmuir wave spectra at Arecibo, Puerto Rico. This mechanism is referred to as a nonlinear scattering of parametric decay instability (PDI)-ex cited Langmuir waves by ''pre-existing'' lower hybrid waves to prefere ntially produce anti-Stokes (i.e., frequency-upshifted) Langmuir waves . Recent radar spectral observations of anti-Stokes Langmuir waves at Arecibo with improved range and time resolution [Sulzer and Fejer, 199 4] can be reasonably understood in terms of this mechanism.