NO. 4 SUN S VARIATION AND TEMPERATURES — ABBOT 2$ 



icity, since they seem to be too large to be due to direct heating 

 changes (for the solar-constant change, as we have seen, is only 0.13 

 percent), may be due to such an indirect solar influence as the altera- 

 tion of the ozone content of the upper air. Theory indicates, and ob- 

 servation confirms, that large percentage fluctuations of the intensity 

 of extreme ultraviolet solar rays occur, and that this produces large 

 fluctuations in atmospheric ozone. Such fluctuations of ozone, operat- 

 ing on the absorption band near lOyu, in the infrared spectrum, would 

 alter the earth's cooling to outer space. I have no means at present 

 of testing the ozone hypothesis. It occurred to me, however, that the 

 fluctuations of the critical frequency of ionization, measured in the 

 Fe layer, might give a clue. 



17. IONIZATION CRITICAL FREQUENCIES 



Dr. Fleming very kindly communicated the hourly Fg values from 

 Huancayo and Watheroo observing stations, 1938 to 1944. I took 

 averages of the daily results for 11 hours of sunlight. These I have 

 averaged by lo-day and monthly intervals for Huancayo. As they 

 may be useful to other investigators, I give them in table 7, which 

 relates only to results from Huancayo. 



As it was very clear that both a yearly periodicity, and a sunspot 

 influence occur in these averages, I tabulated them first for the yearly 

 effect, and then, having removed the best average curve of yearly 

 fluctuation, I plotted the residuals against sunspot numbers. Having 

 obtained the best factor of relationship with sunspot numbers of the 

 residuals remaining from yearly corrections, I removed the sunspot 

 effect also, in order to see if there remained some residuals that would 

 show an irregular march, similar to the march of amplitudes of the 

 temperature effects of the 6.6456-day period. 



For possible use by other investigators I give the march of the 

 yearly fluctuation of 11 -hour daily averages of Fg at Huancayo, Peru, 

 as follows : 



Month Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec. 



Normal Fe 349 350 346 336 321 310 314 324 332 338 342 347 



Also I give the corrections to mean daily (ii daylight hours) F© 

 values for sunspot numbers : 



Sunspot 



number 5 10 jo 30 40 50 60 80 loo 120 140 160 180 200 



Correction 



number — 34 — 30 — 22 — 16 — 10 — 5 +1 12 22 32 42 52 61 71 



