Shifts and asymmetries of lines formed in a thermally driven turbulent medium
Abstract
A simplified theory is proposed for line formation in a turbulent medium when the correlation between the velocity and temperature of the different turbulent elements is introduced. The fact is included that ascending and descending convective bubbles are respectively hotter and cooler than the surrounding medium, a consequence of which is that the population of the lower transition level depends on bubble velocity and source function. Expressions are derived for the absorption and emission coefficients in a microturbulent situation, and it is predicted that lines will be redshifted because, while both coefficients are usually shifted to the blue, the absorption coefficient will be redshifted with respect to the emission coefficient. The theory is applied to the observed asymmetries and shifts of the solar photospheric and chromospheric line profiles. It is concluded that this bubble temperature effect seems to explain the anomalous redshift and its center-to-limb variation as well as other phenomena.
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- February 1975
- Bibcode:
- 1975A&A....38..373S
- Keywords:
-
- Atmospheric Models;
- Atmospheric Turbulence;
- Line Shape;
- Red Shift;
- Solar Atmosphere;
- Temperature Effects;
- Bubbles;
- Cavitation Flow;
- Chromosphere;
- Convective Flow;
- Photosphere;
- Radiative Transfer;
- Thermal Energy;
- Astrophysics