title: Relativistic AC gyromagnetic effects in ultraintense laser-matter interaction.
abstract: We demonstrate that in ultraintense ultrafast laser-matter interaction, the interplay of laser-induced oscillating space-charge fields with laser E and B fields can strongly affect whether the interaction is relativistic or not: stronger laser fields may not in fact produce more relativistic plasma interactions. We show that there exists a regime of interaction, in the relation of laser intensity and incident angle, for which the Brunel effect of electron acceleration is strongly suppressed by AC gyromagnetic fields, at a frequency different from the laser field. Analytically and with 1.5D particle-in-cell modeling, we show that from gyromagnetic effects, even in the absence of usual J x B second-harmonic contributions, there are strong effects on the harmonic emission and on the generation of attosecond pulses.
authors.affiliation: Laboratoire pour l'Utilisation des Lasers Intenses (LULI), Ecole Polytechnique Route de Saclay, 91128 Palaiseau, France. jp@greco2.polytechnique.fr
authors.forename: J P
authors.initials: JP
authors.lastname: Geindre
authors.forename: P
authors.initials: P
authors.lastname: Audebert
authors.forename: R S
authors.initials: RS
authors.lastname: Marjoribanks