  Thanks to their well-defined shape and mostly isolated locations, Bok
globules are suitable objects for studying the physics of low-mass star
formation. To study the magnetic field of the prototypical Bok globule B335, we
obtained a spatially resolved polarization map with SOFIA/HAWC+ at a wavelength
of 214$\,\mu$m. For the first time, these observations reveal that polarization
holes in Bok globules, that is, the decrease in polarization degree towards
their dense centers, also occur in the far-infrared wavelength regime. The
observed polarization pattern is uniform with a mean polarization angle of
48$^\circ\pm $26$^\circ$ and a magnetic field strength of $\sim$ 142$\,\mu$G.
Moreover, we use complementary polarimetic data for B335 obtained at
near-infrared to millimeter wavelengths to analyze and constrain the magnetic
field across different scales. By applying the 3D Monte-Carlo radiative
transfer code POLARIS (Reissl et al. 2016), we developed a model for the
density and magnetic field structure as well as for the dust properties of this
globule. We conclude that the column density towards the center of B335 is too
low to cause the observed polarization hole in B335 via dichroic absorption
(Brauer et al. 2016). Furthermore, we conclude that the effect of
self-scattering has no significant impact on the observed polarization.
Adopting dust-grain alignment via the radiative torque mechanism, a combination
of the interstellar radiation field and the central star as radiation sources
is consistent with the decrease in polarization degree at the outer regions of
B335 ($\approx\,$10$^4\,$au from the core). However, the model fails to explain
the low polarization degree within the inner 5000 au.
