  Magnetic plasma instabilities appear to play an important role in the early
stages of quark-gluon plasma equilibration in the high energy (weak coupling)
limit. Numerical studies of the growth of such instabilities from small seed
fluctuations have found initial exponential growth in their energy, followed by
linear growth once the associated color magnetic fields become so large that
their non-abelian interaction are non-perturbative. In this paper, we use
simulations to determine the nature of this linear energy growth. We find that
the long-wavelength modes associated with the instability have ceased to grow,
but that they cascade energy towards the ultraviolet in the form of plasmon
excitations of ever increasing energy. We find a quasi-steady-state power-law
distribution $f_k \propto k^{-\nu}$ for this cascade, with spectral index $\nu
\simeq 2$.
