Astron. Astrophys. 319, 669-672 (1997)

The helium singlet-to-triplet line ratio in solar prominences

G. Stellmacher ¹ and E. Wiehr <sup>2

1</sup> CNRS; Institut d'Astrophysique, Bd.Arago, F-75014 Paris
² Universitäts Sternwarte Göttingen, D-37083 Göttingen, Germany

Received 24 May 1996 / Accepted 1 August 1996

Abstract

The emissions of the He singlet line at 6678Å and the He triplet line at 4471Å are simultaneously observed in three solar prominences. For two of them, the line pairs He-D₃ / and Ca / were also observed. Comparisons with model calculations show that the emission line ratios require low densities ( cm^-3), low gas pressures (  dyn/cm²), and large physical slab widths. The relative He-to-H number density cannot be much lower than y = 0.1.

Key words: Sun: prominences lines: formation

Send offprint requests to: E. Wiehr

Contents

• 1. Introduction
• 2. Observations
• 3. Results
  • 3.1. Thermal and non-thermal line broadening
  • 3.2. The He singlet-to-triplet ratio
  • 3.3. The He-D₃ -to- ratio
  • 3.4. The Ca -to- ratio
• 4. Discussion and conclusion
• Acknowledgements
• References

© European Southern Observatory (ESO) 1997

Online publication: July 3, 1998
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