  We perform time-dependent, spatially-resolved simulations of blazar emission
to evaluate several flaring scenarios related to magnetic-field amplification
and enhanced particle acceleration. The code explicitly accounts for
light-travel-time effects and is applied to flares observed in the flat
spectrum radio quasar (FSRQ) PKS 0208-512, which show optical/{\gamma}-ray
correlation at some times, but orphan optical flares at other times. Changes in
both the magnetic field and the particle acceleration efficiency are explored
as causes of flares. Generally, external Compton emission appears to describe
the available data better than a synchrotron self-Compton scenario, and in
particular orphan optical flares are difficult to produce in the SSC framework.
X-ray soft-excesses, {\gamma}-ray spectral hardening, and the detections at
very high energies of certain FSRQs during flares find natural explanations in
the EC scenario with particle acceleration change. Likewise, optical flares
with/without {\gamma}-ray counterparts can be explained by different
allocations of energy between the magnetization and particle acceleration,
which may be related to the orientation of the magnetic field relative to the
jet flow. We also calculate the degree of linear polarization and polarization
angle as a function of time for a jet with helical magnetic field. Tightening
of the magnetic helix immediately downstream of the jet perturbations, where
flares occur, can be sufficient to explain the increases in the degree of
polarization and a rotation by >= 180 degree of the observed polarization
angle, if light-travel-time effects are properly considered.
