Stimulated Radiation from Strong Langmuir Turbulence in Ionospheric Modification

New measurements of stimulated electromagnetic emissions (SEE) in low duty cycle heating experiments performed at the HIPAS Observatory are presented. Two distinct types of spectra, a weak diffuse type and a stronger type with deep frequency modulations, were observed. These results have been compared with numerical predictions from a 1D driven and damped Zakharov model and are found to be consistent with Langmuir collapse processes (strong spectra) and Langmuir turbulence of the coexistence type (weak spectra). Through this joint experimental and numerical study, evidence of strong Langmuir turbulence via SEE measurements has been demonstrated. {copyright} {ital 1997} {ital The American Physical Society}