The influence of polarization and charge gradient forces on the dust sheath formation

Abstract

The influence of the polarization and charge gradient forces on the dust sheath formation using a fluid model is investigated. The corresponding new Bohm criterion for the dust sheath formation is obtained. By analyzing the Sagdeev potential numerically, it is found that the polarization and charge gradient forces have opposite effects on the Sagdeev potential and the critical Mach number, i.e., the polarization effect enlarges the width and depth of the Sagdeev potential, while the charge gradient effect narrows the width and depth of the Sagdeev potential. Furthermore, the critical Mach number decreases with the increase in polarization parameter RP and increases with the increase in charge gradient parameter RCG. Finally, regardless of whether the polarization effect or the charge gradient effect is considered, the depth and width of the potential well increase with the increase in the Mach number, while the critical Mach number decreases with the increase in the ratio of ion and electron density ρ.