Optical/UV radiation from accretion disks in quasars is likely to be partly
scattered by a hot plasma enveloping the disk. We investigate whether the
scattering may produce the steep rises in polarization observed blueward of
the Lyman limit in some quasars. We suggest and assess two models. In the
first model, primary disk radiation with a Lyman edge in absorption passes
through a static ionized "skin" covering the disk, which has a temperature
kT similar to 3 keV and a Thomson optical depth tau(T) similar to 1. Electr
on scattering in the skin smears out the edge and produces a steep rise in
polarization at lambda < 912 Angstrom. In the second model, the scattering
occurs in a hot coronal plasma outflowing from the disk with a mildly relat
ivistic velocity. We find that the second model better explains the data. T
he ability of the models to fit the observed rises in polarization is illus
trated with the quasar PG 1630+377.