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MAGNETIC STORMS, SOLAR RADIATION, AND 

 WASHINGTON TEMPERATURE DEPARTURES 



By C. G. abbot 

 Research Associate, S)iiithso>iian Institution 



(With Two Plates) 



Occasionally the earth's magnetic condition is greatly disturbed. 

 At such times large sunspot groups are usually visible near the center 

 of the solar disk. From studies of the aurora, radio transmission, 

 and other electrical phenomena of the atmosphere, it is concluded 

 that the earth is being bombarded by showers of electric ions at times 

 of magnetic storms. These ions appear to emanate most copiously 

 from sunspots. 



For many years the Smithsonian Institution has made daily meas- 

 urements, whenever possible, of the heat equivalent of the energy 

 of solar radiation. It lies mainly in the wave-length region from 

 0.33 to 2.5 microns (thousandths of a millimeter). This embraces 

 ultraviolet, visible, and infrared rays. The measurements are made 

 in such a way that the losses caused by the earth's atmosphere may 

 be estimated. On each day of observation it is computed what the 

 intensity of the sun's heat would be if one could observe at mean 

 solar distance outside the atmosphere. The values thus obtained are 

 termed measures of "the solar constant of radiation." The average 

 value of the solar constant is about 1.94 calories per square centimeter 

 per minute. Fluctuations in solar-constant values occur, but the range 

 of them is small, seldom exceeding i percent of the total. 



The earth's atmosphere on a cloudless day diminishes the intensity 

 of solar heat of the direct sun beam reaching the earth's surface in 

 several ways: First, by the scattering exerted by the molecules of 

 oxygen, nitrogen, and other gases of the atmosphere ; second, by the 

 scattering and absorption produced by dust particles floating in the 

 atmosphere, and seen as haze ; third, by the absorption of rays of 

 certain wave lengths by oxygen, carbon dioxide, water vapor, ozone, 

 and other gases and vapors which produce true absorjition of radia- 

 tion with conversion of radiant energy into heat. About 18S0 [,ord 



SMITHSONIAN MISCELLANEOUS COLLECTIONS, VOL. 110, NO. 6 



