  The Imaging X-ray Polarimetry Explorer (IXPE) observations of the X-ray
binary 4U 1630-47 in the high soft state revealed linear polarization degrees
(PDs) rising from 6% at 2 keV to 10% at 8 keV. Explaining the results in the
framework of the standard optically thick, geometrically thin accretion disk
scenario requires careful fine-tuning of the relevant model parameters. We
argue here that the emission of polarized Bremsstrahlung by anisotropic
electrons in the accretion disk atmosphere can account for the overall high PDs
and the increase of the PDs with energy. We discuss plasma and accretion
effects that can generate electron anisotropies at a level required by the 4U
1630-47 results. We conclude by emphasizing that X-ray polarimetry affords us
the opportunity to obtain information about the magnetization of the accretion
disk atmosphere.
