Computer simulation of the sideband instability

The physical origins of the growth of sidebands of a large amplitude plasma wave are studied numerically. It is shown that in the first phase of the nonlinear evolution of a large amplitude plasma wave the spatially averaged distribution function shows the formation of a stable bump and, for the case presented, the phase velocity of the lower sideband falls on the side of the bump having a positive slope. In the second phase of the evolution of the system, the sidebands saturate and the bumpy region of the spatially averaged distribution function takes a shape close to a flat plateau.