Empirical models of solar magnetic elements: constraints imposed by MgI Stokes profiles.
Abstract
Although the temperature structure of small-scale magnetic features in the lower and middle photosphere has been constrained quite well, there are still considerable uncertainties in the upper photospheric and lower chromospheric thermal structure. As a step towards an improvement of this situation we investigate, using a non-LTE analysis, the diagnostic capabilities of the Stokes I and V profiles of the Mg I b_2_ 517.3nm and the Mg I 457.1nm lines. We find that the V profile of the former line can constrain the magnetic element thermal and velocity structure near the temperature minimum, which goes beyond the capabilities of the commonly used Fe I and II lines. The λ457.1nm line, on the other hand, does not provide any additional information on its own. A comparison of synthetic profiles with plage and network Stokes I and V spectra confirms the findings of Bruls & Solanki (???) that the chromospheric temperature rise starts at a substantially lower height in magnetic elements than in the quiet Sun. Some of the ambiguities in previous empirical models of magnetic elements are also removed. We confirm that small-scale magnetic features are associated with larger line broadening velocities than the quiet Sun, particularly in the higher layers. Finally, the Mg I b_2_ line is revealed to be a direct diagnostic of the merging height of magnetic elements.
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- July 1995
- Bibcode:
- 1995A&A...299..596B
- Keywords:
-
- SUN: MAGNETIC FIELDS;
- SUN: ACTIVITY;
- SUN: FACULAE