Multi-Scale Analysis of Magnetic Fields in Filamentary Molecular Clouds
  in Orion A
  New visible and K-band polarization measurements on stars surrounding
molecular clouds in Orion A and stars in the BN vicinity are presented. Our
results confirm that magnetic fields located inside the Orion A molecular
clouds and in their close neighborhood are spatially connected. On and around
the BN object, we measured the angular offsets between the K-band polarization
data and available submm data. We find high values of the polarization degree,
P_{K}, and of the optical depth, \tau_{K}, close to an angular offset position
of 90^{\circ} whereas lower values of P_{K} and \tau_{K} are observed for
smaller angular offsets. We interpret these results as evidence for the
presence of various magnetic field components toward lines of sight in the
vicinity of BN. On a larger scale, we measured the distribution of angular
offsets between available H-band polarization data and the same submm data set.
Here we find an increase of <P_{H}> with angular offset which we interpret as a
rotation of the magnetic field by \lesssim 60^{\circ}. This trend generalizes
previous results on small scale toward and around lines of sight to BN and is
consistent with a twist of the magnetic field on a larger scale towards OMC-1.
A comparison of our results with several other studies suggests that a
two-component magnetic field, maybe helical, could be wrapping the OMC-1
filament.
