  The magnetic field plays a significant role in the phenomenon of highly
collimated jets of active galactic nuclei (AGN). Relativistic effects prevent
the direct reconstruction of the magnetic field direction as transverse to
electric vectors on radio maps. We determined the topology of the B-field by
modeling the transverse distributions of the total and linearly polarized
intensity, polarization degree, and deviation of the polarization direction
from the local jet axis and by further comparison with observational data. We
consider (i) a helical field with a different twist angle; (ii) a toroidal
field on the jet axis surrounded by a sheath with a longitudinal field. In the
latter scenario, we consider different sheath thickness relative to the spine.
We assumed the sheath velocity is equal to or less than that of the spine. The
relativistic effects have been considered for a general case, under which the
axis and velocity vector of the jet and radial directions do not coincide. Our
simulations reproduce the main features of the observed transverse profiles of
polarization characteristics in parsec-scale AGN jets. The model transverse
distribution shapes of the polarization properties are found to be strongly
influenced by kinematic and geometric parameters of an outflow. We demonstrated
it for three AGNs having different but typical polarization patterns revealed
on radio maps. For each of these objects, we identified the model parameters,
which provide a qualitative correspondence of theoretical profiles with those
obtained from observations, indicating that the B-field is strongly ordered on
parsec scales.
