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Opacity Sources in the UV Spectrum of the Sun

Published online by Cambridge University Press:  30 March 2016

R. M. Bonnet  and
D. Sacotte
R. M. Bonnet
Affiliation:
CNRS Laboratoire de Physique Stellaire et Planétaire, Verrières-le-Buisson, France
D. Sacotte
Affiliation:
CNRS Laboratoire de Physique Stellaire et Planétaire, Verrières-le-Buisson, France

Extract

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In the past three or four years a great deal of attention has been given to the interpretation of the solar UV continuum. Several sets of intensity and limb-darkening measurements made from satellite, rocket and balloon borne instruments are now available, which allow comparisons to be made with theoretical computations. The main purpose of this paper is to discuss these comparisons, we restrict this discussion to the wavelength region between 3000 Å and 1680 Å, in which a significant difference between the observations and the computations still exists. The lines in this wavelength region which are of relevance to the continuum opacity are listed as follows:

the Ly-α line of neutral hydrogen at 1216 Å which appears as a strong emission line;

the resonance doublet of Mgװ at 2795 Å and 2803 Å which causes a broad depression in the solar continuum and shows an emission core similar in shape to the Ly-α line;

the auto-ionization doublet of AlI at 1932 Å and 1936 Å, which appears as two broad absorption features;

several absorption lines such as Mgi 2852 Å Sii 2881 Å;

many FeI and FeII absorption lines.

There are also several discontinuities in the continuum emitted between the lines in the spectrum between 1216 Å and 3000 Å. The most important ones are located at 2500 Å, 2085 Å and 1680 Å, which correspond to the photoionization edges of MgI, AlI and SiI respectively.

Type
III. Joint Discussions
Information
Highlights of Astronomy , Volume 2: Highlights of Astronomy. As presented at the XIVth General Assembly of the IAU, 1970 , 1971 , pp. 495 - 502
Copyright
Copyright © Reidel 1971

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