Profiles of Mg II and Ca II Lines in Nonhomogeneous Chromospheres.
Abstract
Intensity profiles of Ca II and Mg II resonance line cores are calculated for several nonhomogeneous solar atmospheric models at various points across the disk. A self-consistent solution of the radiative transfer and steady-state equations assuming complete redistribution for scattering in the line is separately obtained for each of the two atmospheric components under the usual plane-parallel approximation. Each ion is represented by a model atom consisting of two bound levels and a continuum. Horizontal nonhomogeneity is approximated by a uniform cell enclosed by a rectangular boundary in order to simulate the chromospheric supergranular network. Both cell and boundary models follow the Bilderberg continuum atmosphere out to the temperature minimum. The cell atmosphere is characterized by an isothermal or mildly rising temperature structure from that point outward, whereas the boundary temperature rises much more steeply. Two boundary models (models I and II) based on magnetohydrodynamic studies of the network from a concurrent investigation by one of the authors (R.W.M.), have been investigated in detail. Other chromospheric models are under study. The profiles, which are averages over projected areas of the inhomogeneities, can be made to match the observed reversals in both the Ca and Mg line cores, the limb darkening of the entire Ca K core, and the minimum temperature of 46000K with an optically thick chromosphere. Restrictions placed on the models by observations are discussed.
- Publication:
-
The Astronomical Journal Supplement
- Pub Date:
- 1968
- Bibcode:
- 1968AJS....73R.166B