  The interaction of the two counter-propagating ultrashort laser pulses with a
singular wavefronts in the thin slice of the underdense plasma is considered.
It is shown that ion-acoustic wave is excited via Brillouin three-wave
resonance by corkscrew interference pattern of a paraxial singular laser beams.
The orbital angular momentum carried by light is transferred to plasma
ion-acoustic vortex. The rotation of the density perturbations of electron
fluid is the cause of helical current which produce the kilogauss axial
quasi-static magnetic field. The exact analytical configurations are presented
for an ion-acoustic current field and magnetic induction. The range of
experimentally accessible parameters is evaluated.
