The intensities and profiles of XUV transition zone lines in a quiet sun region compared to a polar coronal hole.
Abstract
The intensities of XUV transition-zone lines from limb spectra of a quiet-sun region and a polar coronal hole are compared. The spectra were obtained with a slit spectrograph on Skylab and cover a region from -12 sec within the limb to 20 sec above it. The lines selected for comparison are formed at temperatures that range from 36,000 to 220,000 K. Lines of the higher-temperature ions, e.g. O v, are significantly less intense in the coronal hole, and lines of lower-temperature ions show little change. Profiles of selected optically thin transition-zone lines from the quiet-sun and coronal-hole spectra are also shown. The lines are broader than expected in ionization equilibrium, and bulk-motion velocities are deduced from the widths of the lines. There appears to be little, if any, statistically significant difference in the velocities obtained from the quiet-sun region and the coronal hole.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- December 1975
- DOI:
- 10.1086/182000
- Bibcode:
- 1975ApJ...202L.147F
- Keywords:
-
- Chromosphere;
- Far Ultraviolet Radiation;
- Solar Atmosphere;
- Solar Corona;
- Electron Transitions;
- Polar Regions;
- Radiant Flux Density;
- Solar Activity;
- Solar Limb;
- Solar Spectra;
- Velocity Measurement;
- Solar Physics