Fast magnetic field annihilation in the relativistic collisionless regime driven by two ultra-short high-intensity laser pulses

The magnetic quadrupole structure formation during the interaction of two ultra-short high power laser pulses with a collisionless plasma is demonstrated with 2.5-dimensional particle-in-cell simulations. The subsequent expansion of the quadrupole is accompanied by magnetic field annihilation in the ultrarelativistic regime, when the magnetic field can not be sustained by the plasma current. This results in a dominant contribution of the displacement current exciting a strong large scale electric field. This field leads to the conversion of magnetic energy into kinetic energy of accelerated electrons inside the thin current sheet.