SUPERPOSITION OF NONLINEAR PLASMA-WAVES

We report results showing that spatially periodic Bernstein-Greene-Kru skal (BGK) waves, which are exact nonlinear traveling wave solutions o f the Vlasov-Maxwell equations for collisionless plasmas, satisfy a no nlinear principle of superposition in the small amplitude limit. The a nalysis explicates the notion of superimposed BGK waves which, as rece nt numerical calculations suggest, is crucial in the proper descriptio n of the time-asymptotic state of a plasma when a large amplitude elec trostatic wave undergoes nonlinear Landau damping.