Exact solution of the problem of quasineutral expansion into vacuum of a localized collisionless plasma with cold ions

An analytical solution of the Vlasov equation for the electrons and the hydrodynamic equations for the ions in a self-consistent electric field is constructed in the quasineutral approximation. This solution is valid for a finite electron-to-ion mass ratio. It permits describing the expansion into vacuum of a collisionless plasma with cold ions and arbitrary initial electron velocity distribution, forming a plasmoid that is bounded and, in the general case, spherically asymmetric in space. Pis’ma Zh. éksp. Teor. Fiz. 67, No. 8, 543–547 (25 April 1998)