Electron vortices produced by ultraintense laser pulses

Particle-in-cell simulations show that finite width and length laser pulses subject to relativistic self-focusing propagate in an underdense plasma in a open-quote open-quote bullet close-quote close-quote shape and produce a quasistatic magnetic field. This field remains behind the pulse and forms a magnetic wake associated with a row of electron fluid vortices which are described by the Hasegawa-Mima equation. The vortices propagate much more slowly than the pulse and evolve into an antisymmetric configuration which is shown to be stable when the distance between its vortices is greater than the electron skin depth. copyright 1996 The American Physical Society