  Gaskell et al. (2007) introduced polarization reverberation mapping as a new
technique to explore the structure of active galactic nuclei. We present
modeling results for the time-dependent polarization signal expected from
scattering inside a centrally illuminated spheroid. Such a model setup
describes a larger corona surrounding the compact source of an active nucleus.
Time-delays between the polarized and the total flux are computed and related
to the geometry of the cloud and the viewing angle. When including the in-flow
dynamics of the cloud, it is possible to constrain its optical depth and
velocity, which enables estimations of the mass inflow rate.
