Emission Lines in the Spectrum of the Solar Corona

Abstract

IT seems very improbable that the bright line spectrum of the inner corona can be attributed to thermal excitation of the coronal matter. We may seek its cause in the process of photoelectric ionisation and apply then, as a first and rough estimate of its brightness, the same analysis as Dr. Zanstra has done in the case of diffuse nebulæ (Astrophys. Jour., 65, No. 1). Thus we assume in this approximation that the emission spectrum of the corona is due to a mechanism of recombination of free electrons with atoms, ionised by the high quantum radiation, emerging from the sun, acting as a black body radiator; and that the corona consists only of monoatomic hydrogen. We have to suppose, further, that the high quantum radiation is completely absorbed by the coronal material, and that all the freed electrons recombine with the ionised hydrogen atoms.