A New Plasma Physics Periodic Kinetic Electrostatic Electron Nonlinear (KEEN) Excitation and its Relation to SEAS (Stimulated Elecron Acoustic Scattering)

ABSTRACT: This topic, new to basic nonlinear plasma physics, is related to and inspired by an important recent result in laser-plasma interaction [1]. This result has been related to the so-called SEAS process [2](Stimulated Electron Acoustic Scattering). Vlasov code simulation studies on our efforts to drive up such waves with an imposed (ponderomotive) driver of limited duration show that long-lived travelling wave excitations (well below the electron plasma frequency and with phase velocities comparable to the electron thermal velocity) only survive only if they are nonlinear and not too weak, with considerable harmonic phase-locked content. We have named these Kinetic Electrostatic Electron Nonlinear waves and find that that (in contrast to previous assumptions) the production of KEEN excitations is not particularly resonant. They thus do not deserve the adjective "acoustic", since they can be driven over a considerable range of velocities. PAPER: In order to understand how waves could be made to exist in the spectral gap between the electron and (combined) ion plasma frequencies, as observed in experiment [1,2], Vlasov-Poisson simulations employing a prescribed ponderomotive driver were undertaken using (because of its lack of noise) an electron Eulerian phase-space-fluid Vlaso