The hydrogen Balmer, Paschen, and Brackett series lines in quiescent prominences

• Published in: Solar physics 1986-08, Vol.106 (2), p.315-333
• Main Authors: ROVIRA, M. G, FONTENLA, J. M
• Format: Article
• Language: English
• Subjects: Astronomy; Earth, ocean, space; Exact sciences and technology; Prominences; Solar physics; Solar system
• ISSN: 0038-0938; 1573-093X
• DOI: 10.1007/BF00158499

To calculate the Balmer, Paschen, and Brackett line intensities, the authors solved the statistical equilibrium equations for a 20-level plus continuum atom of hydrogen. From the temperature, ionization, and the first three-level populations of the prominence models deduced in a previous work, the populations of the 20 bound levels and the integrated intensities corresponding to the series mentioned were calculated. The method was also applied to the Heasley and Mihalas theoretical models. Because the Lyman series are optically thick, two different options were worked out: 1) assume radiative balance in these lines, and 2) correct the radiative rates by multiplying them with an integroexponential function EI2, which depends upon the line optical depth at the thread center. The first option is shown to be the more consistent. The integrated line intensities from the Balmer series have been compared with the observations, and a clear difference was noted between quiescent and active prominences in the sense that the active prominence case cannot be well fitted with the available models. To evaluate the influence of the pressure, the temperature, the thermal conduction coefficient, and the turbulence velocity on the spectrum, the results from different models were compared. The authors conclude that only the lines arising from the lower levels to 8-10 can give information on the physical parameters that characterized the solar prominences since the intensities from the higher members of the series depend only upon atomic properties because of the small departures from LTE of the upper levels involved.