  We reveal the existence of a new type of topological Josephson effect
involving type II superconductors and three-dimensional topological insulators
as tunnel junctions. We predict that vortex lines induce a variant of the
Witten effect that is the consequence of the axion electromagnetic response of
the topological insulator: at the interface of the junction each flux quantum
attains a fractional electrical charge of e/4. As a consequence, if an external
magnetic field is applied perpendicular to the junction, the Witten effect
induces an AC Josephson effect in absence of any external voltage. We derive a
number of further experimental consequences and propose potential setups where
these {quantized, flux induced, Witten} effects may be observed.
