Astron. Astrophys. 358, 728-740 (2000)

Multi-wavelength study of the slow "disparition brusque" of a filament observed with SOHO

B. Schmieder ^1,2, C. Delannée ³, Deng Yuan Yong ⁴, J.C. Vial ⁵ and M. Madjarska <sup>6,7

1</sup> Observatoire de Paris - Section de Meudon, LPSH 2080, 92195 Meudon Principal Cedex, France (Schmieder@mesioa.obspm.fr)
² Institut of Astrophysics, University of Oslo, Blindern, Norway
³ NASA/Goddard Space Flight Center, SOHO EAF, Code 682.3, Building 26, Room G-1, Greenbelt, Maryland 20771, USA
⁴ Beijing Astronomical Observatory, National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012, P.R. China
⁵ Institut d'Astrophysique Spatiale, Université Paris Sud, CNRS, bât. 121, 91405 Orsay, France
⁶ Institute of Astronomy, 72 Tzarigradsko chausse Blvd., 1784, Sofia, Bulgaria
⁷ Armagh Observatory, Armagh BT61 9DG, Ireland

Received 7 February 2000 / Accepted 29 February 2000

Abstract

A mid-latitude filament was observed before and after its eruption with SOHO (EIT, SUMER, CDS and LASCO) and with ground based observatories (Meudon and Pic du Midi) in the context of a coordinated MEDOC campaign in Orsay. The eruption was followed by a large Coronal Mass Ejection well observed by LASCO. Few hours before its eruption, the filament is partially heated (as seen in 195 Å with EIT). The physical conditions of the filament before its eruption have been investigated by spectroscopic analysis of SUMER (the Lyman series L4 to L9) and of CDS combined with the Multi-channel Subtractive Double Pass Spectrograph (MSDP) spectra of H. Five hours before the eruption, large broadenings of chromospheric and transition region lines (CDS) were observed in the main body of the filament suggesting strong turbulence as well as opposite Dopplershifts on each side of the filament (H and He I) which could be interpreted as twist motions. The optical thickness of the filament is rather large. During the eruption the twist is largely developed as observed in 304 Å. The Doppler shifts of the filament estimated from Lyman lines are in good agreement with the velocity of the front edge of the CME bright loop. We notice that both, the filament and the bright loop, are deviated towards the equator. This implies that they belong to the same global expansion event constrained to remain in the equatorial streamer. An X-ray bright point observed close to a filament footpoint could be the signature of reconnection process linked to the destabilization of the filament. It is interpreted in the framework of new MHD modeling of lateral filament footpoints (Aulanier & Démoulin 1998).

Key words: Sun: activity Sun: chromosphere Sun: corona Sun: filaments

Send offprint requests to: B. Schmieder

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Contents

• 1. Introduction
• 2. Observations
  • 2.1. Ground-based instruments
  • 2.2. SOHO instruments
• 3. Overview of the filament
  • 3.1. UV and coronal filament observations
  • 3.2. Bright point
  • 3.3. CME
• 4. Physical parameters of the filament
  • 4.1. Microturbulence and twist before the eruption
  • 4.2. Bulk flows during the eruption
  • 4.3. Optical thickness and gas pressure
• 5. Conclusion
• Acknowledgements
• References

© European Southern Observatory (ESO) 2000

Online publication: June 8, 2000
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