1. Observations of Filament Channels by Hinode/XRT and STEREO
Yingna Su, Adriaan van Ballegooijen, Leon Golub
Harvard-Smithsonian Center for Astrophysics

2. Data Sets
In all, 5 filament eruptions/activations are observed (by STEREO or MLSO) in these 8 filament channels. Post-event arcades are observed (by XRT or STEREO) for 3 of the 5 events.  For 2 of the 5 events, corresponding CMEs are observed by SOHO/LASCO.
Only three possible cavities are observed by XRT or TRACE, while the filament channels are on the limb. The visibility of cavity may be affected by the direction of the filament channels or some bright active regions close by. Any other reason?

3. Observations

4. Sheared Loops within Filament Channels
Filament Channels on the quiet Sun are often observed as dark channels in X-rays and EUV.
Sheared loops within the filament channel can often be observed in X-rays, but not in EUV. Some sheared loops are stable (a couple of days), while others are transient structures (less than 1 hour).

5. Post-event Arcades
Normally, no overlying loops above the filament channel are observed in X-rays and EUV (top panels, prior to filament eruption), but they can be observed as post-event arcades after filament eruptions (bottom panels).
Not all of the filament eruptions/activations are associated with post-event arcades.

6. The emission on the two sides of the filament channels is asymmetric in both X-rays and EUV. One side has curved bright features (white arrows), while the other side (black arrows) has straight faint features.

7. Modeling

8. A nonlinear force-free field model for the filament channel on The filament path is shown on the left panel, and several selected field lines representing the flux rope is shown on the right panel.

9. Side (right panels) and front (left panels) views of selected field lines of the NLFFF model. The field lines at height up to Z=24 are shown on the top.
The field lines in one polarity turn into the flux rope, while the field lines from the other polarity are open or connected to very distant sources.
The observed structures are the feet of the field lines. The density of the higher part of the field lines are too low to be observed.

10. Summary (I)
Filament Channels are often observed as dark channels in X-rays and EUV. Sheared loops within the channel are often seen in X-rays, but not in EUV.
Normally, no overlying loops above the filament channel are observed in X-rays or EUV, but they can be observed as post-event arcades after filament eruptions.

11. Summary (II)
The emission on the two sides of the filament channels is asymmetric in both X-rays and EUV. One side has curved bright features (left), while the other side (right) has straight features.
The 3D magnetic configuration is also asymmetric along the length of the channel. The field lines in one polarity turn into the flux rope, while the field lines from the other polarity are open or connected to very distant sources.