NO. 6 MAGNETIC STORMS ABBOT II 



As Stated above, I find the opposite trend in temperature at Wash- 

 ington to that found by Simpson and Clayton. For I find a depression 

 of temperature following a sudden obscuration of the planet earth, 

 caused by its bombardment by electric ions. The circumstances, how- 

 ever, are not parallel. Those authors treated of a relatively permanent 

 increase of solar radiation. The larger part of the range of the 

 magnetic storm efTect is very short-lived, less than 2 days. Moreover, 

 there is no change of atmospheric transparency to be assumed in the 

 investigations of Simpson and Clayton, except as increased earth 

 temperature presently gives rise to increased atmospheric humidity 

 and greater cloudiness. The magnetic storm, on the contrary, immedi- 

 ately diminishes atmospheric transparency. Any change of cloudiness, 

 which might eventually follow, would doubtless be delayed more than 

 the 9 days after the storm covered by my tabulation. So it seems 

 to me there is no unexplained contradiction between these results 

 and those of Simpson and Clayton. 



NUMBER OF IONS IX A SHOWE-R 



One other point of some interest is an inquiry as to the average 



density of the shower of electric ions for the 53 cases of severe 



magnetic storms covered by table i. The efTect produced was to 



diminish the solar constant by ^ percent. Referring to Annals, volume 



6, figure 11, page 166, the center of gravity of a solar-constant change 



associated with Rayleigh scattering may be set at about wave length 



0.40 micron. On very clear days above Montezuma, with air mass 



i.o, the solar radiation may be observed as high as 1.65 calories per 



0.20 

 square centimeter per mmute, or — =15 percent lower than the 



solar constant. If readers think it worth while, they may compute 

 from Rayleigh's equations, and the above data, the numbers of par- 

 ticles involved under the two sets of circumstances. But roughly 

 estimating, one might say that the 93 million miles of space con- 

 tained —^=0.023 as many particles as would be contained of mole- 

 cules in the atmosphere above Montezuma, where the barometric 

 pressure is about 590 mm. mercury. These figures relate, however, 

 to cases when the great sunspot groups were not central on the sun's 

 disk. The great group of March 1920, produced about 10 times as 

 great an efTect on the solar constant as the average of the 53 cases 

 of 1923 to 1946. 



Using Humphrey's estimate of atmospheric densities, Millikan's 



