Magnetic Field Strengths and Grain Alignment Variations in the Local
  Bubble Wall
  Optical and infrared continuum polarization from the interstellar medium is
known to generally be due to irregular dust grains aligned with the magnetic
field. This provides an important tool to probe the geometry and strength of
those fields, particularly if the variations in the grain alignment
efficiencies can be understood. Here, we examine polarization variations
observed throughout the wall of the Local Bubble, using a large polarization
survey of the North Galactic cap (\textit{b}$>30^\circ$) from
\citet{berdyugin2014}. These data are analyzed together with archival
photometric and spectroscopic data along with the mapping of the Local Bubble
by \citet{lallement2003}. We can model the observational data by assuming that
the alignment driving mechanism is due to the radiation from the surrounding
star field. In particular we find that the fractional polarization is dominated
by the light from the OB associations within 150 pc of the sun, but is largely
insensitive to the radiation field from red field stars. This behavior is
consistent with the expected wavelength dependence of radiative grain alignment
theory. We also probe the relative strength of the magnetic field in the wall
of the Local Bubble using the Davis-Chandrasekhar-Fermi method. We find
evidence for a systematically varying field strength distribution, where the
variations in the field are correlated with the variations in grain alignment
efficiency, indicating that the relatively higher field strength regions might
represent a compression of the wall by the interaction of the outflow in the
Local Bubble and the opposing flows by the surrounding OB associations.
