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ANNUAL REPORT SMITHSONIAN INSTITUTION, 1942 



centers that would otherwise be lost in the jumble of too many story 

 tellers. 



It has long been known that the frequencies of light waves are 

 distorted if there is a powerful magnetic field surrounding the light 

 source. This had been demonstrated in the laboratory shortly after 

 the reason for such a phenomenon had been given by Zeeman in 

 1894. "Wlien the Mount Wilson observers first examined and 

 actually measured the frequency of light coming from the centers 

 of sunspots, it was found to have changed frequency in exactly the 

 way that light weaves are distorted in the laboratory when a power- 

 ful electromagnet is placed around the source of light being ex- 

 amined. If additional proof were needed for the explanation of tho 



Figure 2. — The trend of sunspot activity has been definitely downward since 1937 

 Curve of sunspot numbers smoothed by three months moving averages. 



changed frequencies, it may be stated that the double and triple 

 lines found in the spectrum of sunspots indicated that the light 

 was polarized just as in the case of the polarized light waves coming 

 from the laboratory source upon which the magnetic field is im- 

 pressed. Thus came the startling revelation that sunspots were 

 not only terrific hurricanes but every center was in itself a powerful 

 magnet. Since a magnetic field may exert a repulsing effect upon 

 swiftly moving electrons, we see some reason that charged electric 

 particles can be actually hurled from sunspot centers at velocities 

 which may carry them through space into the earth's atmosphere, 

 thus ionizing the upper regions of the air in a way that would 

 produce auroral displays. In the light of such a mechanism, there- 

 fore, we see a possible reason why aurorae occur in greater numbers 

 and at greater brilliance at times when these solar storms occur 

 most frequently. 



With the new unsurpassed equipment installed at the McMath-Hul- 

 bert Observatory of the University of Michigan, motion pictures of the 



