EXPERIMENTS ON THE NONLINEAR EVOLUTION OF SURFACE-WAVES IN AN OPEN PLASMA WAVE-GUIDE

The nonlinear behaviour of surface waves propagating along a plasma column is investigated. The experiments include (i) measurements of the nonlinear dispersion of the waves and (ii) observation of the evolution of the shape of the wave envelope and of the wave spectrum when the waves are excited with an amplitude-modulated signal. Comparison with theory shows that (i) the measured nonlinear wavelength shift corresponds to increasing wave phase velocity with increasing wave amplitude, (ii) the observed narrowing of the wave envelope can be associated with the formation of periodic nonlinear waves described by dn Jacobi elliptic function solutions of the nonlinear Schrodinger equation and (iii) the observed strong changes of the wave spectrum are mainly related to a nonlinear effect of phase modulation.