TR.I.yS.tTl^iNTlC RADIO TELEPHONE TRANSMISSION 475 



riu- luaniutic ilata have iK-rii sii|)pli«(l through (he courtesy of 

 the Iniled States ("leodetie Siirves . Siinil.ir data taken in lainlaiul 

 were ohtaiiieil from the Kew ol)servator> and sliow similar results. 



The contrast in the diurnal variations of radio transmission liefore 

 • lid after the time a magnetic storm is known to have started, is 



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Fitj. 12 — Correlation of radio transmission and earth's magnetic field — Transmission 



from Rocky Point, U. S. A. (57,000 cycles) to London, Eng. — Earth's magnetic 



field measured at Cheltenham, Md., I'. S. A. 



further brought out in Fig. 13. The lower left-hand curve in this 

 figure superimposes curves of February 22-23 and February 25-26 

 of the previous figure, .\dflitional cases where such marked changes 

 occur are also shown. It will be seen that similar effects exist on the 

 lower frequency of 17 kc. All of these examples are for days of other 

 than maximum magnetic disturbance. In general the effect is to 

 reduce greatly the night-time values and slightly increase the day- 

 light values. The higher peaks in the daylight field strength of 

 Fig. 11 are due to the high daylight values which prevailefl at the 

 time of tiiese disturbances. 



