Abstract:
It has been known for a long time that apart from the visible and heat radiations of Photospheric origin there are other radiations which emanate from the sun and produce notable effects on the earth's atmosphere and on the surface of our planet. Some of these effects, such as the annual means of geomagnetic variations, the frequencies of polar lights, the variations in the brightness of the night sky, the water levels of the different lakes and inland seas, the thickness of the annual rings of trees etc., exhibit a remarkable parallelism with sunspot activity. The object of the present article is not to deal with all these various effects; we shall restrict our considerations mainly to the effects of solar ultraviolet radiation on the outer atmosphere of the earth and on the variations of the geomagnetic field, our principal aim being to derive, from available terrestrial observations, conclusions regarding the nature and the intensity of the ultraviolet radiation emanating from the sun in so far as they seem justifiable on the basis of theoretical considerations and plausible hypotheses.
