THEORETICAL AND SIMULATION STUDIES OF BROAD UP-SHIFTED SIDE-BAND GENERATION IN IONOSPHERIC STIMULATED RADIATION

A second order four-wave parametric process proposed to be responsible for the generation of the broad up-shifted sideband in ionospheric st imulated radiation is studied by using a theoretical model and one dim ensional electrostatic particle-in-cell simulations. The results indic ate that (1) the initial evolution in nonlinear simulations is well de scribed by the proposed theoretical model, (2) the simulation frequenc y power spectrum in a saturated nonlinear state exhibits important cha racteristics of the experimental observations and (3) the full non-lin ear evolution of this four-wave pro cess is crucial in interpreting th e asymmetric nature of the wave frequency spectrum observed during exp eriments.