Nonlinear development of weak beam–plasma instability

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Nonlinear interactions of tenuous electron beam, background, unmagnetized plasma, and self-consistently generated Langmuir and ion-sound waves are analyzed in the framework of plasma weak turbulence kinetic theory. Full numerical solutions of the complete weak turbulence equations are obtained for the first time, which show the familiar plateau formation in the electron beam distribution and concomitant quasi-saturation of primary Langmuir waves, followed by fully nonlinear processes which include three-wave decay and induced-scattering processes. A detailed analysis reveals that the scattering off ions is an important nonlinear process which leads to prominent backscattered and long-wavelength Langmuir wave components. However, it is found that the decay process is also important, and that the nonlinear development of weak Langmuir turbulence critically depends on the initial conditions. Special attention is paid to the electron-to-ion temperature ratio,Te/Ti,and the initial perturbation level. It is found that higher values ofTe/Tipromote the generation of backscattered Langmuir wave component, and that a higher initial wave intensity suppresses the backscattered component while significantly enhancing the long-wavelength Langmuir wave component.

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关键词：

Theoretical or Mathematical/ plasma instability plasma ion acoustic waves plasma kinetic theory plasma Langmuir waves plasma nonlinear processes plasma temperature plasma turbulence plasma-beam interactions/ three-wave decay weak beam-plasma instability nonlinear interactions tenuous electron beam unmagnetized plasma Langmuir waves ion-sound waves plasma weak turbulence kinetic theory numerical solutions plateau formation electron beam distribution concomitant quasisaturation nonlinear processes induced-scattering processes backscattered Langmuir wave components long-wavelength Langmuir wave components electron-to-ion temperature ratio/ A5235P Plasma instabilities A5240M Particle beam interactions in plasma A5235M Nonlinear plasma waves and nonlinear interactions A5235F Plasma electrostatic waves and oscillations A5235D Plasma sound waves, magnetosonic waves A5225D Plasma kinetic equations A5235R Plasma turbulence A5225L Plasma temperature and density