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Session 120 - The Sun.
Oral session, Saturday, January 10
International Ballroom East,
Although it is generally accepted that quiescent filaments have strong horizontal axial magnetic field (Leroy,1984) the field configuration in the legs (``barbs'' or ``feet'') is controversial. Previous observations indicate both rising and falling Doppler motions in such appendages, at speeds less than ``free-fall'' (Dunn,1960; Yi et al,1991; Zirker et al, 1994). Such observations could be consistent with the presence of horizontal magnetic fields that are slowly drifting up and down carrying plasma with them. However the H alpha fine-structure strongly suggests the presence of vertical or highly inclined magnetic field lines. Without vector field observations it is difficult to choose between these alternatives.
In an attempt to clarify the issue, H alpha observations of a quiescent filament were made during its passage across the disk, from 12 to 20 April, 1993 at the Big Bear Observatory.
Remarkable high-speed flows (of order 20 km/s ) were seen along the axial "spine" of the filament. Substantially slower motions were detected in the barbs. The paradox of non-free-fall motions in the predominantly vertically directed threads of barbs, will be discussed briefly.
Bommier,V., Landi Degli'Innocenti,E., Leroy, J-L., and Sahal-Brechot, S.: 1994, Solar Phys. 154,231 Dunn, R.B.,1960, Ph D Thesis, Harvard University Engvold,O.: 1976,Solar Phys.49,283. Leroy,J-L. Bommier,V. nd Sahal Brechot,S.:1984, Astronomy and Astrophysics, 131,33. Yi,Z.,Engvold,O. and Keil,S.L.: 1991, Solar Phys. 132,63. Zirker,J.B.,Engvold,O.and Yi,Z. 1994, Solar Phys. 150,81.
Program listing for Saturday