  We investigate the effects of tidally induced asymmetric disc structure on
accretion onto the white dwarf in intermediate polars. Using numerical
simulation, we show that it is possible for tidally induced spiral waves to
propagate sufficiently far into the disc of an intermediate polar that
accretion onto the central white dwarf could be modulated as a result. We
suggest that accretion from the resulting asymmetric inner disc may contribute
to the observed X-ray and optical periodicities in the light curves of these
systems. In contrast to the stream-fed accretion model for these periodicities,
the tidal picture predicts that modulation can exist even for systems with
weaker magnetic fields where the magnetospheric radius is smaller than the
radius of periastron of the mass transfer stream. We also predict that
additional periodic components should exist in the emission from low mass ratio
intermediate polars displaying superhumps.
