NO. 7 



THE ATMOSPHERE AND THE SUN CLAYTON 



(2) The changes both of short period and of long period in solar 

 radiation are related to visible changes in the number and area of 

 spots, faculae and flocculi seen on the sun. 



(3) The changes in solar radiation are correlated with other phe- 

 nomena such as certain changes in terrestrial magnetism, in radio- 

 receptivit}', and meteorological changes which are known by other 

 evidence to be related to solar conditions. 



The critics of solar variability have pointed out that the measured 

 variations have decreased as the accuracy of the observations in- 

 creased and that in the earlier observations the eflfects of water vapor 



DAYS BEFORE 



4 2 



DAYS AFTER 



1.952 



1.951 I 



1.950 



1.949 



1.946 



1.947 



1.946 



\ f fo.>,4 t f t r f Y r ]\f 



of aun 



Fig. I. — Calcium flocculi and solar radiation. The mean values of solar 

 radiation received at the earth in calories per square centimeter per minute on 

 days before and days after the passage of calcium flocculi across the central 

 meridian of the sun. 1918-1920. Flocculi of 400 or more on the Fbro scale of 

 values. 



in the air, of dust, of ozone, and of turbidity were not entirely 

 eliminated ; but they have in no manner destroyed or impaired these 

 fundamental evidences of variability. 



Abbot and his associates ' have given evidence of the relation of 

 solar radiation changes to solar contrast and to groups of spots on 

 the sun, Fowle ' has shown a relation to groups of flocculi, and I * 

 have shown a relation to faculae. Bauer * has shown a relation to cer- 

 tain changes in terrestrial magnetism, and Austin ' has found a 



' Smithsonian Misc. Coll., Vol. 66, No. 5, 1916. 



" Idem, Vol. 77, No. 5, 1925. 



'Idem, Vol. 77, No. 6, p. 53, 1925. 



^ Terr. Mag., Vol. 20, pp. 143-158, Dec, 1915. 



' Smithsonian Misc. Coll., Vol. 80, No. 2, p. 13, 1927. 



