  We present a study on the structure of quiescent filament channels observed
by Hinode/XRT and STEREO/EUVI from December 2006 to February 2009. For 10
channels identified on the solar disk, we find that the emission on the two
sides of the channel is asymmetric in both X-rays and EUV: one side has curved
bright features while the other side has straight faint features. We interpret
the results in terms of a magnetic flux rope model. The asymmetry in the
emission is due to the variation in axial magnetic flux along the channel,
which causes one polarity to turn into the flux rope, while the field lines
from the other polarity are open or connected to very distant sources. For 70
channels identified by cavities at the limb, the asymmetry cannot be clearly
identified.
