Localized Fields and Density Perturbations Due to Self-Focusing of Nonlinear Lower-Hybrid Waves

Large-amplitude lower-hybrid wave bursts at ω₀>ω_LH are excited from a grid and propagate into a density gradient perpendicular to B-->₀. The evolution of the internal rf fields and the plasma parameters is investigated. Above threshold localized field maxima appear (E_int>>E_appl) and, simultaneously, strong density perturbations are formed. The nonlinear phenomena are interpreted by ponderomotive-force and space-charge separation effects.