Non-linear free streaming in Vlasov plasma

On the basis of a fully non-linear numerical solution of the Vlasov-Poisson equation we demonstrate that in the Fourier transformed velocity space the free streaming is a non-linear multimode phenomenon. In the transformed space the oscillatory part of the disturbance (plasma oscillations) is uncoupled from its free streaming part (the one that in the linearized treatment escapes into infinity) but the free streaming part is strongly coupled to plasma oscillations. It exercises a complicated movement in the Fourier transformed phase plane accompanied by dispersion.