SUN SPOTS AND KADIO— STETSON 



227 



general lifting of the ionization level in the earth's atmosphere may 

 be expected to continue with fluctuations through the next three years, 

 but in 1934 solar activity should be as quiescent as at tlie last mini- 

 mum in 1923. 



With the assistance of Marvin Cobb, nearly 3,000 hours of recording 

 data have accumulated to date (January, 1932), which is making 

 rapidly available a store of material for more extensive investigations. 



Through an analj^sis of existing data it has become possible to de- 

 termine the percentage change of intensity of signal strengths as a 

 function of the distance of the receiving station from the subsolar 



/too (^ 



zcoo^ 



Zfoo 



Z800 



3ZOO 



FiGCRE 12. — Correlation of radio reception and sun spots from observations recorded 

 at Perkins Observatory 1030 and 1931 



point. This makes it possible to apply important corrections for twi- 

 light observations which enter into part of the records during the 

 summer months. These corrections have already served to minimize 

 some of the less obvious departures in radio reception from the ex- 

 pected values which follow generally the inverse trend of sun-spot 

 numbers. 



An examination of three years' radio data has revealed the appar- 

 ent dependence of the intensity of reception upon the position of the 

 moon in the sky at the hour of observation, radio reception in gen- 

 eral showing 100 per cent increase in strength at those times when 

 the moon is well below the horizon. 

 102992—32 16 



