DEPARTURES FROM THERMODYNAMIC EQUILIBRIUM IN CHROMOSPHERIC MAGNESIUM I, CALCIUM I, AND OXYGEN I

An observational and theoretical study is combined for the purpose of investigating departures from thermodynamic equilibrium in neutral magnesium, calcium, and oxygen in the solar chromosphere. The observational data are reduced from 1952 eclipse plates taken by the High Altitude Observatory staff. From the comparison of line intensities, it is possible to show that the population of the energy levels of Mg I and O I depart from a Boltzmann distribution. These departures are in the same sense as those found for helium, that is, the population of the metastable triplet level or quintet for O I is enhanced relative to the population of the excited singlet levels triplets O I. A search for similar effects between upper triplet and singlet states of Ca I does not indicate significant departures from the Boltzmann distribution. Author