Hydrodynamic regime and cold plasmas hit by short laser pulses

TL;DR

This paper explores conditions for a hydrodynamic description of cold plasma impacted by ultra-short, intense laser pulses, using a relativistic model to analyze wave-breaking and electron acceleration.

Contribution

It introduces a relativistic plane model that reduces complex PDEs to simpler Hamilton equations, enabling analysis of wave-breaking in cold plasma under intense laser impact.

Findings

Conditions for hydrodynamic description established

Wave-breaking localized via Jacobian inequality

Model simplifies analysis of electron acceleration mechanisms

Abstract

We briefly report and elaborate on some conditions allowing a hydrodynamic description of the impact of a very short and arbitrarily intense laser pulse onto a cold plasma, as well as the localization of the first wave-breaking due to the plasma inhomogeneity. We use a recently developed fully relativistic plane model whereby we reduce the system of the Lorentz-Maxwell and continuity PDEs into a 1-parameter family of decoupled systems of non-autonomous Hamilton equations in dimension 1, with the light-like coordinate $\xi=ct\!-\!z$ replacing time $t$ as an independent variable. Apriori estimates on the Jacobian $\hat J$ of the change from Lagrangian to Eulerian coordinates in terms of the input data (initial density and pulse profile) are obtained applying Liapunov direct method to an associated family of pairs of ODEs; wave-breaking is pinpointed by the inequality $\hat J\le 0$. These results may help in drastically simplifying the study of extreme acceleration mechanisms of electrons, which have very important applications.