The magnetic nature of wide EUV filament channels and their role in the mass loading of CMEs

¹ Observatoire de Paris, LESIA, 92195 Meudon Cedex, France e-mail: brigitte.schmieder@obspm.fr
² University of Oslo, ITA, PO Box 1029, Blindern, 0315 Oslo, Norway

Corresponding author: G. Aulanier, guillaume.aulanier@obspm.fr

Received: 26 November 2001
Accepted: 23 January 2002

Abstract

Previous works have shown that dark and wide EUV filament channels observed at Å  are due to absorption of EUV lines in cool plasma condensations that are not observed in . We extend this interpretation and we address the issue of the possible injection of their mass into CMEs, through the magneto-hydrostatic modeling in 3D of one filament observed both in and in EUV. The model parameters are fixed so as to match the observations only. Further comparison of the model with the EUV observations reveal the magnetic nature of the absorbing plasma condensations. They are formed in magnetic dips, as for the filament itself. Opacity ratios and the hydrostatic condition imply that the dips must be filled by cool material up to 1700 km, which increases the filament mass by 50% as compared to estimations. Far from the filament, the absorbing condensations are located below 4 Mm in altitude above the photosphere, on the edge of weak photospheric parasitic polarities, within the lower parts of long field lines overlaying the filament. By physical analogy with filament feet, we redefined these extended regions as EUV feet. The broadening of the EUV filament channel is dominated by EUV feet, while the larger filling of dips plays a non-negligible but minor role. Further implications from this work are discussed, on the visibility and the geometry of the condensations, on the existence of EUV filament channels in the absence of filaments, on the loading of cool material into filament feet through bald patch reconnection and on the complex geometry of the upper prominence-corona transition region. The magnetic topology implies that during the filament eruption, the mass of its wide EUV feet will not contribute to the CME, whereas the extra mass provided by the large filling of dips in the filament flux tube will be loaded into the CME.