  We study the coupled Wong Yang-Mills equations for both U(1) and SU(2) gauge
groups and anisotropic particle momentum distributions numerically on a
lattice. For weak fields with initial energy density much smaller than that of
the particles we confirm the existence of plasma instabilities and exponential
growth of the fields which has been discussed previously. Also, the SU(2) case
is qualitatively similar to U(1), and we do find strong ``abelianization'' of
the non-Abelian fields during the period of exponential growth. However, the
effect nearly disappears when the fields are strong. This is because of the
very rapid isotropization of the particle momenta by deflection in a strong
field on time scales comparable to that for the development of Yang-Mills
instabilities. This happens without entropy production which makes it very
interesting for the phenomenology of high-energy heavy-ion collisions.
