  Velocity gradients in a stellar atmospheric plasma have an impact on the
anisotropy of the radiation field that illuminates each point within the
medium, and this may in principle influence the scattering line polarization
that results from the induced atomic level polarization. Here we analyze the
emergent linear polarization profiles of the Ca II infrared triplet after
solving the radiative transfer problem of scattering polarization in
time-dependent hydrodynamical models of the solar chromosphere, taking into
account the impact of the plasma macroscopic velocity on the atomic level
polarization. We discuss the influence that the velocity and temperature shocks
in the considered chromospheric models have on the temporal evolution of the
scattering polarization signals of the Ca II infrared lines, as well as on the
temporally averaged profiles. Our results indicate that the increase of the
linear polarization amplitudes caused by macroscopic velocity gradients may be
significant in realistic situations. We also study the effect of the
integration time, the microturbulent velocity and the photospheric dynamical
conditions, and discuss the feasibility of observing with large-aperture
telescopes the temporal variation of the scattering polarization profiles.
Finally, we explore the possibility of using the differential Hanle effect in
the IR triplet of Ca II with the intention of avoiding the characterization of
the zero-field polarization to infer magnetic fields in dynamic situations.
