COHERENT PHENOMENA IN THE RELAXATION OF A DIFFUSE ELECTRON-BEAM IN OPEN PLASMA SYSTEMS

New results obtained in numerical: modeling of the collisionless proce sses in beam-plasma systems with nonequilibrium electron velocity dist ribution are presented. The systems are described by the Vlasov-Poisso n equations. Calculations were pel formed by using grid splitting sche mes. It is shown that, for a sufficiently large wave amplitude (large enough for the enhancement of the wave-beam correlations and formation of the coherent spatial-temporal structure), the quasilinear relaxati on turns out to be unstable; therefore, the quasilinear theory fails t o describe the plasma dynamics and turbulent transport in most of the open plasma systems. A typical example is the classical problem of a d iffuse electron beam steadily injected into the half-space filled by p lasma. In this case, the self-consistent the plasma transport processe s and deserve testing in laboratory experiments. A brief review of the current state of the problem is presented.