686 



BELL SYSTEM TECHNICAL JOURNAL 



Very striking and significant results were obtained when seasonal 

 averages of magnetic activity and radio field strength were plotted in 

 Fig. 4 to indicate seasonal trends. Except for the magnetic sub- 

 maximum in May the curves of field strength and magnetic activity 



2.0 1.8 



y>|.9 1.7 



1.7 1.5 



5 < < 



1.5 



h 0.7 



I 0.6 

 O 



O 



z 

 o 



I 0.4 



502LU 

 It 



26"g 



^ > 



^5 



JAN FEB MAR APR MAY JUNE JULY AUG SEPT OCT NOV DEC JAN FEB 



Fig. 4 — Seasonal averages of long-wave radio field strength conii)ared with 

 solar phenomena and terrestrial magnetic activity. 



