Population mechanisms for the He(+) N = 3 levels determined from measurements of the solar 1640 A emission
Abstract
The intensities of the 3s-2p, 3p-2s, and 3d-2p components of the He II 1640 Å line have been measured from solar data taken by the NRL slit spectrograph on Skylab. The relative and absolute population densities of the 3s, 3p, and 3d levels of He+ are determined near the white-light limb in various solar regions (coronal hole, quiet Sun, active regions, and a prominence) and in a flare region on the solar disc. The population density measurements are interpreted using a rate equation model for the He+ ion. It is found that self-absorption of the 3p-1s radiation contributes to the population of the 3p level in all the solar regions that are studied and is particularly important in the active regions, the prominence and the flare. Recombination contributes to the population of the 3d level in the active regions near the limb and in the prominence. In all the solar regions that are studied, the 3p-2s component of the 1640 Å line is more intense than the 3d-2p and 3s-2p components.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- March 1985
- DOI:
- 10.1093/mnras/213.3.417
- Bibcode:
- 1985MNRAS.213..417S
- Keywords:
-
- Coronal Holes;
- Helium Ions;
- Population Theory;
- Radiative Recombination;
- Solar Spectra;
- Ultraviolet Spectra;
- Atomic Energy Levels;
- Atomic Excitations;
- Electron Density (Concentration);
- Recombination Reactions;
- Self Absorption;
- Solar Flares;
- Solar Prominences;
- Stellar Coronas;
- Solar Physics