  Due to the quick evolution of the solar chromosphere, its magnetic field
cannot be inferred reliably without accounting for the temporal variations of
its polarized light. This has been broadly overlooked in the modelling and
interpretation of the polarization due to technical problems (e.g., lack of
temporal resolution or of time-dependent MHD solar models) and/or because many
polarization measurements can apparently be explained without dynamics. Here,
we show that the temporal evolution is critic for explaining the spectral-line
scattering polarization because of its sensitivity to rapidly-varying physical
quantities and the possibility of signal cancellations and attenuation during
extended time integration. For studying the combined effect of time-varying
magnetic fields and kinematics, we solved the 1.5D NLTE problem of the second
kind in time-dependent 3D R-MHD solar models and we synthesized the Hanle and
Zeeman polarization in forward scattering for the chromospheric {\lambda}4227
line. We find that the quiet-sun polarization amplitudes depend on the
periodicity and spectral coherence of the signal enhacements produced by
kinematics, but that substantially larger linear polarization signals should
exist all over the solar disk for short integration times. The spectral
morphology of the polarization is discussed as a combination of Hanle, Zeeman,
dynamic effects and partial redistribution. We give physical references for
observations by degrading and characterizing our slit time-series in different
spatio-temporal resolutions. The implications of our results for the
interpretation of the second solar spectrum and for the investigation of the
solar atmospheric heatings are discussed.
