  We consider a pp-wave symmetric model in the framework of the
Einstein-Maxwell-aether-axion theory. Exact solutions to the equations of axion
electrodynamics are obtained for the model, in which pseudoscalar, electric and
magnetic fields were constant before the arrival of a gravitational pp-wave. We
show that dynamo-optical interactions, i.e. couplings of the electromagnetic
field to a dynamic unit vector field, attributed to the velocity of a cosmic
substratum (aether, vacuum, dark fluid...), provide the response of axionically
active electrodynamic system to display anomalous behavior.
