Variation of the solar He I 1830 A line: 1977 - 1980
Abstract
Daily measurements of the equivalent width of the 10830 A He I line integrated over the visible disk show: (1) an increase from about 32 to about 74 mA in the monthly mean values from the minimum to the maximum of the current solar cycle; (2) the monthly mean values are more smoothly varying than most other indices of solar activity; (3) rotation modulates the daily values in a highly variable manner with amplitudes as large as plus or minus 20%; (4) the apparent synodic rotation period is 29 days rather than the expected 27 days associated with active regions; (5) despite great differences in the appearance of the sun in 3933 A Ca I and 10830 A He I, the central intensity of the former correlates with the equivalent width of the latter with a value r = 0.97.
- Publication:
-
NASA Conference Publication
- Pub Date:
- December 1981
- Bibcode:
- 1981NASCP2191..265H
- Keywords:
-
- Coronas;
- H Lines;
- Solar Activity;
- Solar Constant;
- Solar Rotation;
- Solar Spectra;
- Variations;
- Calcium;
- Emission Spectra;
- Helium;
- Luminosity;
- Solar Physics;
- Stellar Spectra;
- Solar Physics