Self-similar expansion of collisionless plasmas with heated electrons.

We present a self-similar model for the planar expansion of a semi-infinite, collisionless plasma with externally heated electrons. The plasma is modeled as a 2-fluid system of electrons and cold ions and the effect of charge separation is included through the self-consistent electrostatic field given by the Poisson equation. Qualitatively different regimes of the expansion are observed as the thermal energy and the amount of the charge separation are varied. A scale invariance is observed for the self-similar dispersive hydrodynamic system, and the global structure of the solutions is analyzed. The model is used to obtain quantitative estimates for the expansion dynamics of laser-heated plasmas, in terms of the laser-pulse parameters and heating mechanisms.