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

The magnetic quadrupole structure formation during the interaction of two ultrashort 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 cannot 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.