Nonlinear screening of a point-like charge in a collisionless plasma

Abstract

Solutions of the nonlinear Poisson equation are analyzed and compared with the Debye formula based on a linear approximation. A deficit in the charge density is shown to exist in a perturbed plasma in comparison with the linear consideration. As a result, the nonlinear screening proves to be weaker than the linear one, so the region of exponential decrease in the electric potential is shifted to longer distances from the external charge. The presence of a trapped particle population favors screening and thereby improves the applicability of the approximate Debye expression. By this means, a clear understanding of the kinetic structure of the charge induced in a polarized plasma is very important for a correct physical interpretation of the screening as a general property of plasmas.