Finite amplitude Langmuir oscillations in a plasma resonance region

Stimulated Langmuir oscillations of an inhomogeneous plane plasma layer in an external harmonic h.f. field are considered in the multi-fluid hydrodynamics approximation. Restriction of the electric field amplitude near the plasma resonance point is investigated which is due to linear transformation into plasma waves, self-intersection of electron trajectories, anharmonism of Langmuir oscillations and nonstationarity of the plasma for various density profiles. Generation of plasma waves and acceleration of particles on wavebreaking of resonance leading to efficient dissipation of the oscillation energy in the resonance region are studied numerically. The role of ion motion induced by striction forces is analyzed qualitatively. The conditions are indicated under which modulation, parametric etc. instabilities related to ion movement, are negligible