Theoretical investigation of the helium absorption line λ1083 nm in the atmosphere of the quiet sun.
Abstract
The profile of the neutral helium absorption line λ1083 nm is calculated using the model quiet solar atmosphere and compared with the observed profile. A line formation mechanism is proposed. It is stressed that the line is not a simple superposition of the chromospheric emission line and the photospheric absorption line in accordance with the temperature gradient sign in the chromosphere and photosphere. Actually the optical thickness in this line begins to exceed the corresponding optical thickness in the continuum just in the chromosphere though the absorption line itself forms in the photosphere. Center-to-limb variations of the line in different features, from the hottest to the coolest ones, are qualitatively explained in terms of the model atmosphere adopted for these features. An effort is made to explain theoretically the center-to-limb behavior of the line and the transformation of the absorption line into emission one.
- Publication:
-
Kinematics and Physics of Celestial Bodies
- Pub Date:
- 1993
- Bibcode:
- 1993KPCB....9d..63B