  The effect of an externally applied flow on symmetry degenerated waves
propagating into opposite directions and standing waves that exchange stability
with the traveling waves via mixed states is analyzed. Wave structures that
consist of spiral vortices in the counter rotating Taylor-Couette system are
investigated by full numerical simulations and explained quantitatively by
amplitude equations containing quintic coupling terms. The latter are
appropriate to describe the influence of inversion symmetry breaking
perturbations on many oscillatory instabilities with O(2) symmetry.
