On the Relations Between Ionosphere, Sunspots and Solar Corona

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Abstract
Analysis of the ultra-violet solar radiation producing the ionospheric layers E, F 1 and F 2 , particularly its correlation to sunspots and coronal intensities in λ 5303, shows that for wave-lengths λ < 700 A. the inner corona is about 10 5 times brighter than the photosphere and that its total intensity varies during a solar cycle by a factor of the magnitude 10. The variations of intensity, which are superposed on a constant background-brightness (permanent corona) arise from extended, long-lived bright coronal patches, whose total intensity is controlled, with a certain delay, by the underlying spot groups. The distribution of brightness within these regions corresponds roughly to the reverse of the one observed in λ 5303. With increasing wave-length, that is approaching the end of the Lyman-continuum ( λ ∼800–912), the intensity of the corona reverts to that of the chromospheric faculae, whose intensity, apart from a negligible limb darkening, follows the development of the spot group under it with a delay of a few days. At L α ( λ 1215) the chromospheric faculae and particularly the eruptions once again define the total intensity of the Sun.

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