The Abundance of Helium in Prominences and in the Chromosphere
Abstract
The abundance of helium relative to hydrogen is spectroscopically determined in prominences and in the chromosphere by using 1952, 1958, 1962 and 1966 eclipse data. Care is taken in the intensity calibration of emission lines, the self-absorption, and the departure from local thermodynamic equilibrium. We find from the line profiles and intensities of prominences and the chromosphere that the neutral helium lines are emitted in the metal-hydrogen emitting region where the kinetic temperature is low enough, 6000 ∼ 8000 K, so that only the ionization due to UV radiation from the corona can explain the intensity of neutral helium emission. Also we find that the intensity ratio of HeI 3888.65 to H8 3889.05 increases towards the upper boundaries of prominences and of the chromosphere and that it approaches to a universal limiting value, both in various prominences or in the chromosphere, where it is considered that the ionization of neutral helium and hydrogen is nearly complete. From these facts the helium to hydrogen number ratio is found to be 6.5 ± 1.5%.
- Publication:
-
Solar Physics
- Pub Date:
- September 1971
- DOI:
- 10.1007/BF00146066
- Bibcode:
- 1971SoPh...19..384H
- Keywords:
-
- Hydrogen;
- Helium;
- Transition Region;
- Emission Line;
- Thermodynamic Equilibrium