Filament channel structures in a SiIV line related to a 3D magnetic model

A recent 3D magnetic model of filament support (Aulanier and Demoulin, 1998 ) has shown that specific morphologies derived from the model, based on SOH O/MDI magnetograms, match quite well with the observations of a filament ob served in H alpha and Ca II lines with the German telescope VTT in Tenerife on 25 September 1996 (Aulanier et al., 1998, 1999a). Some predictions of t his model concern the filament channel. To continue the comparison of model and data, we have investigated the same filament region observed in ultrav iolet by the SOHO spectrometers SUMER and CDS. The elongated EUV fine struc tures in the filament channel observed in the Si iv 1393.76 Angstrom line b y SUMER have similar orientations and locations to features predicted by th e model of Aulanier et al. (1999a). These regions are near the bases of fie ld lines which tangentially join to the photosphere in so called 'bald patc hes' and are parts of large arcades above the filament channel. In addition , we consider the Si IV Doppler shifts in these structures and compare them to what might be expected from the model field structure. Our study also s uggests that the filament has a very low opacity in Si IV, lower than that of the O V line observed by CDS.