Line width observation of He ii 4686 Å and He i 4713 Å in the chromosphere
Abstract
Line profiles of He II 4686 Å and He I 4713 Å from active regions in the chromosphere were observed during the total solar eclipse of February 16, 1980, with a grazing incidence objective grating spectrograph. The Doppler width of the He I triplet line of 4713 Å increases with height and the average width is compatible with width of metallic and hydrogen lines, suggesting that the kinetic temperature of He I triplet emitting region is T ≦ 8000 K. This can only be explained by recombination after photo-ionization due to coronal UV radiation. The Doppler width of the Paschen α line of He II 4686 is, without any correction for the separation of subcomponents of the line nor non-thermal velocity, 18.4 km s-1. This line width also shows a tendency to increase with height. After comparison with Doppler widths of He I 4713 and the EUV lines, and a necessary subtraction of non-thermal velocity, it is shown that this line is emitted in a 2 × 104 K temperature region, which again supports the view that this line is emitted through the recombination process after photoionization due to coronal XUV radiation below 228 Å.
- Publication:
-
Solar Physics
- Pub Date:
- February 1984
- DOI:
- 10.1007/BF00173957
- Bibcode:
- 1984SoPh...90..291H
- Keywords:
-
- Atomic Energy Levels;
- Chromosphere;
- Helium;
- Spectral Line Width;
- Ultraviolet Spectra;
- Photoionization;
- Solar Corona;
- Solar Eclipses;
- Solar Physics;
- Recombination;
- Active Region;
- Temperature Region;
- Line Width;
- Line Profile