The coronal temperature and nonthermal motions in a coronal hole compared with other solar regions.
Abstract
The coronal lines Si VIII (1446 A), Fe X (1463 A), Fe XI (1467 A), and Fe XII (1242 A and 1349 A) were observed above the limb over a quiet region, a coronal hole, and two active regions. The lines emitted at temperatures greater than 1 million K; i.e., the iron lines, are not observed in the coronal-hole spectra, so the indication is that in the coronal hole most of the plasma is at a temperature of less than 1 million K. The emission measures and column densities of the lines are derived from available atomic cross-section data, and the results are discussed. The nonthermal velocities in the coronal hole and quiet region are about 20 km/s. The velocities in the active regions are substantially less.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- March 1977
- DOI:
- 10.1086/182394
- Bibcode:
- 1977ApJ...212L.143D
- Keywords:
-
- Far Ultraviolet Radiation;
- Plasma Temperature;
- Solar Corona;
- Solar Spectra;
- Emission Spectra;
- Flow Velocity;
- Forbidden Bands;
- Iron;
- Silicon;
- Solar Limb;
- Solar Physics