Ion-acoustic waves in weakly ionized plasmas with charge-exchange collisions

Abstract

Ion-neutral charge-exchange collisions in plasmas of laboratory, space, and astrophysical origins are fundamental to understanding wave dissipation and wave generation phenomena. This paper implements a charge-exchange collision operator in the Boltzmann–Poisson system equations for a weakly ionized plasma. When considering an electric field perturbation, the governing kinetic equations provide significant results concerning the plasma conductivity and the dielectric function, appearing in simple, sensible forms. The present analysis reveals a backward wave propagation phenomenon at maximum conductivity when the wavenumber of the plasma wave is smaller than the reciprocal of the ion-neutral collisions mean free path. In addition, it is shown that ion-neutral coupling resulting from charge-exchange collisions enhances ion-acoustic waves below and beyond the ion plasma frequency and leads to the onset of a fundamental instability that overcomes Landau damping under certain circumstances. The collisionless model is recovered as a limiting case, i.e., in the asymptotic limit of a long mean free path.

Nonplanar ion acoustic waves in e-p-i plasmas with non-Maxwellian distributed electrons and positrons

“…Numerous scientific articles have comprehensively addressed the fundamental characteristics of ion acoustic waves (IAWs), including Landau damping, propagation, dispersion relation, etc [1][2][3][4][5]. We have chosen to explore this problem in nonplanar geometry using more sophisticated frameworks that capture some of the minute details of the IAWs, as there are some novel and fascinating features of the IAWs.…”