Drift effects on forced oscillations of a plane geometry plasma with the multiple water bag model

Considers electrostatic longitudinal oscillations of an infinite, hot, homogeneous, non collisional plasma. The plasma is excited by a monopolar or a dipolar infinite plane grid, mechanically not coupled to the medium. The drift motion is uniform and perpendicular to the excitation plane. The analytical-numerical model M.W.B. (Multiple Water Bag) presents, for drift values equal or larger than the thermal speed, dispersion branches locally not monotonous, with poles alternatively real or complex, varying rapidly with the excitation frequency. The determination of the nature of the contributions (upstream or downstream) is a tricky problem, and for some frequencies a very important 'noise of model' can be introduced.