Influence of particle distribution function on plasma expansion into vacuum

Influence of velocity distribution of plasma particles in its expansion into the vacuum is studied. For this purpose, the one-dimensional Vlasov-Poisson system of equations is solved in planner geometry for both electrons and ions. Real value of electron-to-ion mass ratio is considered and electron and ion temperatures are assumed to be equal. It is shown that, a part of the initial internal energy is devoted to the particle arrangement in the velocity space and therefore, the expansion rate and the electric field of charge separation decrease.