Densities in the quiet sun and polar coronal holes from EUV line ratios involving O III (1666.15 Å).
Abstract
The EUV line intensity ratios C iii (1908.73 A)/o iii (1666.15 A), 0 iii (1666.15 A)/Si iv (1402.77 A), and C iii (1908.73 A)ISi iv (1402.77 A) are shown to be sensitive to variations in the electron density at densities typical of the quiet Sun ( 1010 cm - at 6 x 10 K). Using the 0 iii line, the above ratios can be normalized to observational data and densities in quiet-Sun regions and coronal holes can be determined. The average value of the density determined for three quiet-Sun regions is 1.9 x 1010 cm - . The densities determined from several observations of the north and south polar coronal holes are about the same as in the quiet Sun, with the exception of one set of observations of the north polar hole that indicates a density about a factor of 2 less than that of the quiet Sun. Subject headings: Sun: corona - Sun: spectra - ultraviolet: spectra
- Publication:
-
The Astrophysical Journal
- Pub Date:
- December 1978
- DOI:
- 10.1086/156689
- Bibcode:
- 1978ApJ...226.1129D
- Keywords:
-
- Coronal Holes;
- Electron Density (Concentration);
- Far Ultraviolet Radiation;
- Line Spectra;
- Oxygen Spectra;
- Solar Atmosphere;
- Ultraviolet Spectra;
- Atomic Excitations;
- Carbon;
- Ratios;
- Silicon;
- Solar Activity;
- Solar Physics;
- Electron Densities:Solar Coronal Holes;
- Extreme UV:Solar Coronal Holes;
- Extreme UV:Solar Spectrum