Search

PHOTOGRAPHS of the solar spectrum made with the vacuum spectrograph of the McMath–Hulbert Observatory have revealed a variety of interesting and complex features in the structures of the Fraunhofer lines1. The appearance of the hydrogen line cores suggests an underlying, diffuse component that evidently originates in the photosphere, upon which are superposed a series of streaks that must be of chromospheric origin. The weaker metallic lines (of Rowland intensity less than about 10) also fluctuate in width and intensity and have a characteristic zig-zag appearance caused by the Doppler shifts of ascending and descending gas columns which are associated with the granulation in the photosphere.