Nonlinear electromagnetic phenomena in the relativistic interaction of ultrahigh intensity laser pulses with plasmas

2D, low-frequency, relativistic solitary waves have been found recently in 2D. Particle-in-cell simulations of ultra-intense laser pulses propagating in underdense plasmas, in regimes where the laser pulse undergoes energy de pletion and downshifting of its frequency. These slowly propagating, spatia lly localized, electromagnetic structures represent an important channel of energy conversion from the laser pulse to the plasma. Pulse energy can als o be converted into fast propagating structures, associated with collimated beams of ultrarelativistic electrons. Lienard-Wiechert magnetic field stru ctures have been observed in PIC simulations to move together with focalize d ultrarelativistic electron beams in the plasma.