  We report on spectropolarimetric observations across the Mg II h and k-lines
at 2800 angstrom made by the Ultraviolet Spectrometer and Polarimeter onboard
the Solar Maximum Mission satellite. Our analysis confirms the strong linear
polarization in the wings of both lines observed near the limb, as previously
reported, but also demonstrates the presence of a negatively (i.e., radially
oriented) polarized signal between the two lines. We find evidence for
fluctuations of the polarization pattern over a broad spectral range, resulting
in some depolarization with respect to the pure scattering case when observed
at very low spatial and temporal resolutions. This is consistent with recent
theoretical modeling that predicts this to be the result of redistribution
effects, quantum interference between the atomic levels of the upper term, and
magneto-optical effects. A first attempt at a quantitative exploitation of
these signals for the diagnosis of magnetic fields in the chromosphere is
attempted. In active regions, we present observations of circular polarization
dominated by the Zeeman effect. We are able to constrain the magnetic field
strength in the upper active chromosphere using an analysis based on the
magnetograph formula, as justified by theoretical modeling. We inferred a
significantly strong magnetic field (~500 G) at the 2.5 sigma level on an
exceptionally active, flaring region.
