Etudy of the linear and nonlinear regimes in an unmagnetized electron-ion plasma.

Abstract

In order to study how the dynamics of an unmagnetized Maxwellian electron plasma is modified by the presence of mobile positive heavy ions, the present work aims to study the regimes of damped and nonlinear perturbations in a driftless Maxwellian electron-ion plasma, considiring a mass ratio mi/me = 1836.153 and charge ratio qi/|qe| = 1.0, specifically in the range of low frequencies (ωr ≤ 0.2ωpe) and velocities in the order of the ion acoustic phase velocity vφ,IA for the excited wavenumber, primarily for the temperature ratio Ti/Te = 1.0. Also, the response of the plasma is studied for different temperature ratios Ti/Te above and below Ti/Te = 1.0. The whole study is accomplished through numerical simulations of the Vlasov-Poisson system of equations using spectral interpolation in position and velocity, and symplectic integration in the time dependency. It is expected that in the case of damped perturbations both Langmuir and ion acoustic waves propagate relatively independent from each other and exhibit opposite behaviors in the velocity range of interest, whereas in the nonlinear case, electrostatic solitary waves are expected to arise due to the presence of heavy mobile ions related to electron trapping and ion acoustic solitons. It is expected that dynamics related to the ions is accentuated with lower ratios Ti/Te.