  We have investigated the relaxation of a hydrostatic hot plasma column
containing toroidal magnetic field by the Current-Driven (CD) kink instability
as a model of pulsar wind nebulae. In our simulations the CD kink instability
is excited by a small initial velocity perturbation and develops turbulent
structure inside the hot plasma column. We demonstrate that, as envisioned by
Begelman, the hoop stress declines and the initial gas pressure excess near the
axis decreases. The magnetization parameter \sigma, the ratio of the Poynting
to the kinetic energy flux, declines from an initial value of 0.3 to about 0.01
when the CD kink instability saturates. Our simulations demonstrate that
axisymmetric models strongly overestimate the elongation of the pulsar wind
nebulae. Therefore, the previous requirement for an extremely low pulsar wind
magnetization can be abandoned. The observed structure of the pulsar wind
nebulae do not contradict the natural assumption that the magnetic energy flux
still remains a good fraction of the total energy flux after dissipation of
alternating fields.
