  Laser beams with Laguerre-Gaussian (LG) mode carry orbital angular momentum
(OAM), however when interacting with plasmas, the net OAM acquired by plasmas
is basically zero after interaction. Here, we find when there exist a small
magetostatic seed along laser propagation direction, the barrier would be
broken, giving rise to dramatic OAM transfer from LG lasers to plasmas. Hence,
the net OAM remained in plasmas system would continuously enhance the
magetostatic field, until the corresponding Larmor frequency of electrons is
comparable to the laser frequency in vacuum. Three-dimensional particle-in-cell
(3D-PIC) simulations are performed to confirm our theory, producing
space-uniform, time-stable and extremely intense magetostatic fields.
