Intense magnetic field generation by relativistic ponderomotive force in an underdense plasma

Abstract

It is shown that the relativistic ponderomotive force exerted by an ultra intense laser pulse launched in a plasma could generate a very strong low frequency (with index 1f hereafter) magnetic field B1f with a maximum value of the order of B1f/B1 = ωpe/ω, where ωpe is the electron plasma frequency and ω the laser one, and B1 the high frequency magnetic field of the laser pulse. We derive the mechanism for this B1f-field creation in an underdense plasma and show how to diagnose its presence and propose an experimental set-up to achieve the measurement. We also stress the universality of this detection as far as picosecond pulses and the far infrared radiation range (FIR) are concerned. The great influence of this B1f-field on related important phenomena, such as relativistic self-focusing and wakefield generation by short laser pulses, is briefly underlined.