Ion thermal double layers in a pair-ion plasma containing charged dust impurities

We investigate the formation and dynamics of ion thermal double layers (ITDLs) in a plasma, composed of positive and negative ions as well as a fraction of stationary charged (positive or negative) dust impurities. By using the hydrodynamic and Poisson equations for the two ion species, a modified Korteweg–de Vries equation (mKdV) has been derived. The mKdV equation admits double layer solution. It is found that ITDLs profile is significantly affected by the presence of positively/negatively charged dust impurities. Also, the temperature ratio between the negative-to-positive ions plays an important role in deciding the polarity of the ITDLs. In the dust free case, the system supports only rarefactive double layers for any possible values of the temperature ratio. This investigation can be useful for future research on pair-ion plasmas.