Phase-mixing of Langmuir oscillations in cold electron-positron-ion plasmas

Abstract

Space-time evolution of Langmuir oscillations in a cold homogeneous electron-positron-ion plasma has been analyzed by employing a straightforward perturbation expansion method, showing phase-mixing and, thus, wave-breaking of excited oscillations at arbitrary amplitudes. Within an assumption of infinitely massive ions, an approximate phase-mixing time is found to scale as ωpetmix∼[(6/δ2){(2−α)5/2/(1−α)}]1/3, where “δ” and “α” (= n0i/n0e) are the amplitude of perturbation and the ratio of equilibrium ion density to equilibrium electron density, respectively, and ωpe∼4πn0ee2/m is the electron plasma frequency. The results presented on phase-mixing of Langmuir modes in multispecies plasmas are expected to be relevant to laboratory and astrophysical environments.