Hydrodynamic approach to the interaction of a relativistic ultrashort laser pulse with an underdense plasma

The interaction of an ultrashort, high peak power laser pulse with an underdense plasma is investigated within a physical model based on the three-dimensional cold hydrodynamic approach, which allows one to study the dynamics of the laser pulse and of the generated wakefields self-consistently, in the fully relativistic, strongly nonlinear regime. Our model is developed with the aim of describing very short laser pulses (with l0<lp and l0<<lperp , where l0 ,lperp ,lp are the pulse length, its transverse scale, and the plasma wavelength, respectively) down to single cycle radiation wave packets, which have become available with the recent progress in laser technology. The space-time structure and the evolution of large quasistatic electric and magnetic fields are studied, together with the pulse dynamics, by the direct numerical integration of the relativistic fluid and field equations, within the extended paraxial approximation.