Reciprocal interparticle attraction in complex plasmas with cold ion flows

The paper investigates, in the framework of the kinetic approach, the linear screening of a point non-absorbing charge in a homogeneous collisionless plasma with cold ion flow. The velocity distribution of ions far from the charge is assumed to be a shifted Maxwellian distribution with infinitesimal thermal velocity and finite flow velocity, and the electron component is considered as a homogeneous neutralizing background. The potential in the direction perpendicular to the flow is found to have an attractive part (i.e. two like charges aligned perpendicular to the flow can attract each other electrostatically). The paper addresses in detail the relevance of the model to the screening of charged dust particles levitated in the plasma-wall transition layer. In particular, by using the Bohm collisionless sheath model the paper shows that in certain cases electrons do not contribute significantly to the screening of dust particles: deep in the non-neutral sheath the electron density is much smaller than the ion density, and in the quasineutral presheath (well above the sheath entrance) kinetic energies of ions are small as compared with the electron temperature. Also, the model of the present paper is shown to be in agreement with existing measurements of the interaction potential between two dust particles aligned perpendicular to the ion flow in the plasma-wall transition layer of a radio-frequency discharge (Konopka U et al 2000 Phys. Rev. Lett. 84 891) and predicts a minimum of the interaction potential to be located outside the distance range in which the measurements were performed.