The longitudinal motion of electrons and waves in plasmas with an ultraintense laser field

Abstract

A simplified model is proposed for the longitudinal electron motion in homogeneous plasmas with a linearly polarized laser field. Based on its numerical solution, an approximate analytic solution is obtained. The approximate solution is made up of several components and their physical meanings are explained. Numerical comparison indicates that our model is consistent with the Akhiezer–Polovin model under the chosen initial conditions. By investigating the reliability of the analytic solution, the solution is found to be valid for small and intermediate plasma densities. The corresponding electron trajectories are presented and the influence of the electrostatic field is discussed. In addition, the electrostatic field with different components is obtained and the component related to electron plasma frequency is found to be important. The influence of the electron longitudinal motion on the ultraintense electromagnetic wave itself is also investigated, the components with different frequencies are constructed, and some of them are proved to be stronger than the third order harmonic one. Futhermore, a new dispersion relation of the ultraintense pumping field is given, with which the simplified model is more reliable.