Radiation from electromagnetically driven Langmuir turbulence

A two‐level model for the interaction between the electromagnetic pump wave and the electrostatic turbulence is formulated for ionospheric radio modification experiments. On the local level, the Zakharov equations, or similar models, apply. The interaction with the global electromagnetic level is represented by a second‐order current density averaged over the local spatial variable. The energy exchange between the local and global level is represented by a Joulean product involving this second‐order current density. The global generation problem is solved in the simplest cases. The escaping energy flux in the sideband ω is shown to be represented as a folding between the power spectrum of the local source and a squared Airy function. This power spectrum has been calculated from numerical simulations of electromagnetically driven Langmuir turbulence, using a one‐dimensional model of the Zakharov type, for varying values of the parameters. For parameters in the cascade range, narrow line structured spectra were obtained, while for parameters in the cavitation range, very broad featureless spectra were obtained. Comparison with recent experimental stimulated electromagnetic emissions data did not confirm a signature for the existence of cavitation in the experiments.