  Physical vacuum is a special superfluid medium populated by enormous amount
of virtual particle-antiparticle pairs. Its motion is described by the modified
Navier-Stokes equation: (a)~the pressure gradient divided by the mass density
is replaced by the gradient from the quantum potential; (b)~time-averaged the
viscosity vanishes, but its variance is not zero. Vortex structures arising in
this medium show infinitely long lifetime owing to zero average viscosity. The
nonzero variance is conditioned by exchanging the vortex energy with zero-point
vacuum fluctuations. The vortex has a non-zero core where the orbital speed
vanishes. The speed reaches a maximal value on the core wall and further it
decreases monotonically. The vortex trembles around some average value and
possesses by infinite life time. The vortex ball resulting from topological
transformation of the vortex ring is considered as a model of a particle with
spin. Anomalous magnetic moment of electron is computed.
