Zero-mass-electrons limits in hydrodynamic models for plasmas

We study the zero-mass-electrons limits in the hydrodynamic models for plas mas consisting of electrons and ions. We prove, under suitable assumptions, that the evolution of the ions is governed by the Euler equations coupled with a nonlinear Poisson equation, as the mass of electrons tends to zero. (C) 1999 Elsevier Science Ltd. All rights reserved.