TY  - BOOK
AU  - Lites,Bruce William
TI  - Observation and analysis of the solar neutral iron spectrum
PY  - 1972///
CY  - Colorado
PB  - University of Colorado
KW  - Solar atmosphere
KW  - Spectrum, Solar
KW  - Iron
KW  - Spectra
N1  - Thesis (Ph. D.) -- University of Colorado
N2  - In this work the solar neutral iron spectrum is studied in order to 1) understand the conditions of excitation and ionization of the neutral iron atom in the solar atmosphere, and 2) ascertain what may be learned about the solar atmosphere from mean (spatial and time averaged) profiles of representative neutral iron lines. 
The mean solar profiles of 18 neutral iron lines of varying strengths were obtained at high dispersion and at several positions from the center of the solar disk to the limb. These profiles were analyzed from the standpoint of kinetic equilibrium in neutral iron ionization and excitation equilibrium leads to these general results: 
1. Most of the strong FeI lines, as well as many of the weaker lines of FeI, are formed at heights in the atmosphere where departures from local thermodynamic equilibrium (LTE) are large.
2. Deviations from the Saha ionization equilibrium between FeI and FeII are large in the temperature minimum region, however the excitation equilibrium of FeI satisfies the condition of detailed balance below the temperature minimum.
3. Deviations from LTE prescribe only a small upward revision of the estimate to the solar iron abundance given by LTE curve-of-growth analyses. 
4. Opacities in the principal bound-free continua of neutral iron are large enough to make neutral iron a significant solar opacity source between 1500 Å and 2000 Å. 
The comparison of the synthesized and observed center-to-limb behavior of the neutral iron line profiles led to the following results:
5. The far wings of the strong lines indicate a photospheric iron abundance of 1.5 x 10-5 ± 0.5 x 10-5 relative to hydrogen. 
6. The electron density in the region of the initial temperature rise in the chromosphere necessary to fit the cores of the strong FeI lines is comparable to the electron densities derived from eclipse measurements.
7. An anisotropic (angle-dependent) non-thermal broadening velocity, or microturbulence, is necessary to explain the observed FeI line core profiles, and the broadening from a macroturbulent (large scale) velocity aids in explanation of some of the finer details of the observed line core profiles.
ER  -