  The optical radiation and polarization signatures in blazars are known to be
highly variable during flaring activities. It is frequently argued that shocks
are the main driver of the flaring events. However, the spectral variability
modelings generally lack detailed considerations of the self-consistent
magnetic field evolution modeling, thus so far the associated optical
polarization signatures are poorly understood. We present the first
simultaneous modeling of the optical radiation and polarization signatures
based on 3D magnetohydrodynamic simulations of relativistic shocks in the
blazar emission environment, with the simplest physical assumptions. By
comparing the results with observations, we find that shocks in a weakly
magnetized environment will largely lead to significant changes in the optical
polarization signatures, which are seldom seen in observations. Hence an
emission region with relatively strong magnetization is preferred. In such an
environment, slow shocks may produce minor flares with either erratic
polarization fluctuations or considerable polarization variations, depending on
the parameters; fast shocks can produce major flares with smooth PA rotations.
In addition, the magnetic fields in both cases are observed to actively revert
to the original topology after the shocks. All these features are consistent
with observations. Future observations of the radiation and polarization
signatures will further constrain the flaring mechanism and the blazar emission
environment.
