  We present new observations of the active star-formation region NGC 1333 in
the Perseus molecular cloud complex from the James Clerk Maxwell Telescope
B-Fields In Star-forming Region Observations (BISTRO) survey with the POL-2
instrument. The BISTRO data cover the entire NGC 1333 complex (~1.5 pc x 2 pc)
at 0.02 pc resolution and spatially resolve the polarized emission from
individual filamentary structures for the first time. The inferred magnetic
field structure is complex as a whole, with each individual filament aligned at
different position angles relative to the local field orientation. We combine
the BISTRO data with low- and high- resolution data derived from Planck and
interferometers to study the multiscale magnetic field structure in this
region. The magnetic field morphology drastically changes below a scale of ~1
pc and remains continuous from the scales of filaments (~0.1 pc) to that of
protostellar envelopes (~0.005 pc or ~1000 au). Finally, we construct simple
models in which we assume that the magnetic field is always perpendicular to
the long axis of the filaments. We demonstrate that the observed variation of
the relative orientation between the filament axes and the magnetic field
angles are well reproduced by this model, taking into account the projection
effects of the magnetic field and filaments relative to the plane of the sky.
These projection effects may explain the apparent complexity of the magnetic
field structure observed at the resolution of BISTRO data toward the filament
network.
