A new type longitudinal plasma waves induced in an isotropic plasma with a superstrong short laser pulse

Abstract

A description of propagation of relativistically intense short laser pulse into an isotropic plasma is presented. A kinetic equation for a spectral function of electromagnetic waves is derived for an arbitrary amplitude of pump wave, fully relativistic case is considered. The resulting kinetic equation of spectral function is used along with the set of equations of the plasma to study the several type of instabilities and the importance of relativistic effects is pointed out. In the case of a superstrong short laser pulse a novel Langmuir waves, with phase velocities larger than the speed of light, are revealed in an underdense plasma, and the waves of ion-sound type, which damp only on ions, are found in an overdense plasma.