  A modified method is presented to generate artificial magnetic turbulence
that is used for test-particle simulations. Such turbulent fields are obtained
from the superposition of a set of wave modes with random polarizations and
random directions of propagation. First, it is shown that the new method
simultaneously fulfils requirements of isotropy, equal mean amplitude and
variance for all field components, and vanishing divergence. Second, the number
of wave modes required for a stochastic particle behavior is investigated by
using a Lyapunov approach. For the special case of slab turbulence, it is shown
that already for 16 wave modes the particle behavior agrees with that shown for
considerably larger numbers of wave modes.
