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 r adio modification experiments. On the local level, the Zakharov equati ons, or similar models, apply. The interaction with the global electro magnetic level is represented by a second-order current density averag ed over the local spatial variable. The energy exchange between the lo cal and global level is represented by a Joulean product involving thi s second-order current density. The global generation problem is solve d in the simplest cases. The escaping energy flux in the sideband omeg a is shown to be represented as a folding between the power spectrum o f the local source and a squared Airy function. This power spectrum ha s been calculated from numerical simulations of electromagnetically dr iven Langmuir turbulence, using a one-dimensional model of the Zakharo v type, for varying values of the parameters. For parameters in the ca scade range, narrow line structured spectra were obtained, while for p arameters in the cavitation range, very broad featureless spectra were obtained. Comparison with recent experimental stimulated electromagne tic emissions data did not confirm a signature for the existence of ca vitation in the experiments.