Volume 432, Number 2, March III 2005
|Page(s)||699 - 704|
|Published online||02 March 2005|
On the formation of the He I 10 830 Å line in a flaring atmosphere
Department of Astronomy, Nanjing University, Nanjing 210093, PR China
2 Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing 210008, PR China
Accepted: 1 November 2004
We explore the formation of the He i 10 830 Å line in a flaring atmosphere, with special attention to the nonthermal effects of an electron beam. Using non-LTE calculations we obtain the line profiles from different model atmospheres. Without the nonthermal effects, the line changes from weak absorption in a cool atmosphere to emission in a hot and condensed atmosphere, as expected. However, the presence of an electron beam can significantly change the line strength, producing much stronger absorption and emission in these two cases. We find that in the nonthermal case, the collisional ionization of He i followed by recombinations becomes an important process in populating the triplet levels corresponding to the He i 10 830 Å line. These results suggest that the He i 10 830 Å line is also a potential diagnostic tool for nonthermal effects in solar or stellar flares.
Key words: line: profiles / Sun: atmosphere / Sun: flares / stars: atmospheres
© ESO, 2005
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