Astronomy and Astrophysics – Astrophysics
Scientific paper
Sep 1993
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1993a%26a...276..219c&link_type=abstract
Astronomy and Astrophysics, Vol. 276, p. 219 (1993)
Astronomy and Astrophysics
Astrophysics
29
Sunspot, Line: Formation, Magnetic Fields
Scientific paper
We have studied the formation of the Na I and K I resonance lines in a sunspot umbra looking at their diagnostic value.
We have computed different cross-sections and rates for the excitation of the alkali atoms by collisions with neutral hydrogen atoms in addition to electrons, and we have evaluated their effects on the emergent line profiles.
The main results of the line synthesis, which allowed for different temperature structures, line blend, the Zeeman broadening produced by a constant vertical magnetic field, and a possible overcorrection for stray light of the observed spectrum, are that:
i) the comparison between the observed and the computed inner wings of the sodium profiles suggests that the umbral upper photosphere is cooler than in a standard model;
ii) there is no satisfactory fit of the reversed and asymmetric line cores of the sodium and potassium resonance lines in the umbral spectrum.
Caccin Bruno
Gomez M. T.
Severino Giuseppe
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