Polarization of synchrotron emission from relativistic reconfinement
  shocks with ordered magnetic fields
  We calculate the polarization of synchrotron radiation produced at the
relativistic reconfinement shocks, taking into account globally ordered
magnetic field components, in particular toroidal and helical fields. In these
shocks, toroidal fields produce high parallel polarization (electric vectors
parallel to the projected jet axis), while chaotic fields generate moderate
perpendicular polarization. Helical fields result in a non-axisymmetric
distribution of the total and polarized brightness. For a diverging downstream
velocity field, the Stokes parameter U does not vanish and the average
polarization is neither strictly parallel nor perpendicular. A distance at
which the downstream flow is changing from diverging to converging can be
easily identified on polarization maps as the turning point, at which
polarization vectors switch, e.g., from clockwise to counterclockwise.
