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Prominence Emission Lines Observed With SUMER and Two Ground-based Telescopes

Published online by Cambridge University Press:  12 April 2016

C.R. de Boer ,
G. Stellmacher  and
E. Wiehr
C.R. de Boer
Affiliation:
Max-Planck-Institut für Aeronomie, D–37191 Katlenburg-Lindau, Germany
G. Stellmacher
Affiliation:
Institut d’Astrophysique, 78bis Boulevard d’Arago, F–75014 Paris, France
E. Wiehr
Affiliation:
Universitäts-Sternwarte, Geismarlandstr 11, D–37083 Göttingen, Germany

Abstract

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Two sets of H, He, and Ca+ emission lines were observed in a quiescent prominence simultaneously with the VTT and the Gregory telescope on Tenerife. At the same time, SUMER took two scans of low-ionized EUV emission lines.

The emission ratios of Ca+–to–Balmer lines from ground vary little in the prominence, indicating a largely constant gas-pressure. In contrast, the ratio of He–to–Balmer from the ground shows the (known) increase toward the prominence borders, indicating higher temperature there. Similarly, the two-dimensional distributions of the ratios S IV/N II and C III/He I show pronounced bright prominence rims.

The reduced He 537Å and He 584Å line widths are 2.6 and 3.6 times larger, respectively, than those of He D3 and He 3888Å. Explaining this by the optical thickness yields τ 0 = 104 and τ 0 = 2 · 105 for the two EUV lines. The total He 584 emission amounts to 13 watt/m2 ster in the main prominence body where the D3 line yields 4 watt/m2 ster; existing models, however, predict a factor 0.18.

The widths of simultaneously observed optical lines with different atomic weights yield thermal and non-thermal broadening parameters of Tkin ≈ 8000 K and 2.5 < ξ < 6.5 km/s. The EUV lines, however, show line widths which correspond to much higher temperatures and non-thermal velocities. Assuming for each ion the corresponding ionization temperature, the line widths require non-thermal velocities of 15–40 km/s which is similar to values for the quiet corona.

Type
Filaments and Their Environment
Information
International Astronomical Union Colloquium , Volume 167: New Perspectives on Solar Prominences , 1998 , pp. 196 - 200
Copyright
Copyright © Astronomical Society of the Pacific 1998

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