Simulation study of radiation generation by upper-hybrid waves in space plasmas

In planetary magnetospheres and in the Earth's ionosphere, continuum radiation has been frequently observed. By employing a semi-theoretical model and a Vlasov simulation code, it is shown that electromagnetic slow X (or Z) waves can be nonlinearly excited by a large amplitude upper-hybrid pump. In our process, the latter decays into electromagnetic and lower-hybrid waves. The growth rate of the parametric instability is numerically calculated and compared with simulation results from a direct Vlasov code. Both semi-theoretical and simulation results are in good agreement.