The University of Michigan Centimeter-Band All Stokes Blazar Monitoring
  Program: Single-Dish Polarimetry as a Probe of Parsec-Scale Magnetic Fields
  The University of Michigan 26-m paraboloid was dedicated to obtaining linear
polarization and total flux density observations of blazars from the mid-1960s
until June 2012 providing an unprecedented record tracking centimeter-band
variability over decades at 14.5, 8.0, and 4.8 GHz for both targeted objects
and members of flux-limited samples. In the mid-1970s through the mid-1980s,
and during the last decade of the program, observations were additionally
obtained of circular polarization for a small sample of radio-bright (S>5Jy),
active sources. Key program results include evidence supporting class-dependent
differences in the magnetic field geometry of BL Lac and QSO jets,
identification of linear polarization changes temporally associated with flux
outbursts supporting a shock-in-jet scenario, and determination of the spectral
evolution of the Stokes V amplitude and polarity for testing proposed models.
Recent radiative transfer modeling during large flares supports a jet scenario
with a kinetically-dominated, relativistic flow at parsec scales with embedded
turbulent magnetic fields and dynamically-weak ordered components which may be
helical; the circular polarization observations are consistent with
linear-to-circular mode conversion within this turbulent jet environment.
