kinetic simulation of vacuum plasma expansion beyond the “plasma approximation”

Summary: introduction/purpose: one of the key approaches to solving an entire class of modern plasma physics problems is the so-called plasma approximation. the most general definition of the plasma approximation is a theoretical approach to the electric field calculation of a system of charges under the electric quasi-neutrality condition. the purpose of this paper is to compare the results of the numerical simulation of the kinetic processes of the quasi-neutral plasma bunch expansion to the analytical solution of a similar kinetic model but in the plasma approximation. methods: the given results are obtained by the methods of deterministic modeling based on the numerical solution of the system of vlasov-poisson equations.results: the provided comparison of the analytical expressions for the solution of kinetic equations in the plasma approximation and the numerical solutions of the vlasov-poisson equations system convincingly show the limitations of the plasma approximation in some important cases of the considered problem of plasma formation decay. conclusion: the theoretical results of this work are of great importance for understanding the shortcomings of the plasma approximation, which can manifest themselves in practical applications of computational plasma physics.