Abstract
Nonlinear forced oscillations in a cold electron plasma are treated in Lagrangean form, and exact equations for the density and the velocity are derived. In the absence of the forcing term, we have Konyukov's result but not Amer's and Amer's error is shown. According to the Coddington and Levinson's method, the existence conditions of the periodic solut on of these equations are given.
As a typical example of the forcing term, the case of F=-m (νv+βv3) +C sin ωt is treated and for β=0, we find that the density tend to n0 as, t→∞, while in the velocity there remains only the forced oscillation.Also, for β≠0we have essintially the same result, and the density converges to n0 and the periodic solution of the velocity corres-ponds to the forced oscillation.
