Analysis of the chromospheric hydrogen spectrum at the 1962 eclipse

Slitless spectrograms of the chromosphere obtained during the eclipse of 4–5 February 1962 have been analyzed to obtain the decrements of the level populations of hydrogen, the self-absorption in the Balmer lines, and parameters useful in construction of models of the low chromosphere.The decrement of the high energy levels of hydrogen inferred under the optically thin assumption does not vary significantly with height, and it appears to be unnecessary to seek large deviations from local thermodynamic equilibrium in the high levels. The observed Balmer-to-Paschen line intensity ratios have been used to infer self-absorption and opacities in the Balmer lines. The resulting population of the second energy level is about an order of magnitude smaller than that found by Athay and Thomas from the 1952 data.The chromospheric continuum was generally underexposed; the absence of observed continuum in the visible region of the spectrum made it impossible to derive a unique model from the 1962 data alone. However, the high Balmer line data and new theoretical solutions of the statistical equilibrium equations for hydrogen combined with corrected 1952 observations at 4700 A are compatible with a model having approximately the same temperature and neutral hydrogen structure as the 1952 model by Pottasch and Thomas but half the electron density: T _e = 6200K, N ₁ = 7.4 × 10¹³ cm^-3, N _e = 2.3 × 10¹¹ cm^-3 at 500 km and T _e = 7200K, N ₁ = 2.6 × 10¹² cm^-3, N _e = 1.7 × 10¹¹ cm^-3 at 1000 km.Based in part on a Ph.D. thesis submitted to the Department of Astro-Geophysics, University of Colorado.Now at the Department of Astronomy, Indiana University.