Large-amplitude ion-acoustic double layers in multispecies plasma

Abstract

We have investigated the effect of second-ion species on the characteristics of a large-amplitude ion-acoustic double layers (IADL) in a collisionless, unmagnetized plasma consisting of hot and cold Maxwellian populations of electrons and two cold-ion species with different masses, concentrations, and charge states. After deriving the criteria for the existence of large-amplitude IADL, we find that the presence of a positive-ion impurity does not modify considerably the characteristics of large-amplitude IADL. However, the presence of a negative-ion impurity changes significantly the characteristics of large-amplitude IADL. We have also presented an analytic discussion of small-amplitude IADL using a reductive perturbation method.