The EIT images confirm that there is little temperature contrast. Off the limb, the EIT images show the cavity and core very clearly. The filament is seen very well. A close study of the SXT images when the structure is about 45 degrees east of central meridian shows a number of fine loops that lie high over the neutral line. The loops evolve over times of hours.
Similar structure is visible in a movie made near the central meridian.
A specific issue is the reason for the sharp boundary of the cavity. A series of SXT images show the boundary varies in sharpness over hours, sometimes appearing as an structure that is brighter than the corona immediately above it. Extrapolation of the surface magnetic fields assuming potential fields would likely reproduce the overall loop arcade over the polar boundary neutral line. But the nearly detached appearance of the cavity almost certainly requires nonpotential fields. Stretching of fieldlines by differential rotation across the neutral line is large at this latitude.