THE 

 LONDON, EDINBURGH, and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



KNAL OF SCIENCE. 





[SIXTH SERIES.] 



DECEMBER 1919. 



LXX. Xote on the Theory of Magnetic Storms. By 

 F. A. Lindemanx, Professor of Experimental Philosophy , 

 Oxford *. 



THERE seems to be no doubt that terrestrial magnetic 

 storms are connected in some way with solar distur- 

 bances. It would seem, however, that all the theories so far 

 put forward break down when the quantities are considered. 

 The object of this note is to put forward a tentative 

 suggestion which does not appear to lead to any inconsistent 

 result quantitatively even though, like the other theories, 

 it involves some assumptions. The best way to approach 

 the subject is probably by criticising the theory now 

 probably most generally accepted, which has been most 

 elaborately worked out by Dr. Chapman. The recognition 

 of the fact that a radial current on the earth would explain 

 the magnetic phenomena is undoubtedly a most valuable 

 advance, and with this part of his theory it is not proposed 

 to tamper. There are, however, a number of other points 

 which render his hypothesis untenable, and a clear under- 

 standing of these seems to lead inevitably to the theory put 

 forward in this note. 



Dr. Chapman assumes that beams of a rays are emitted 

 by parts of the solar surface and that the earth is subjected 

 to a magnetic storm when it passes through a beam of this 

 sort. The a rays are supposed to penetrate to a height of 

 about 10 7 cm. above the earth's surface, spread out into 



* Communicated bv the Author. 

 Phil Mag. S. 6. Vol. 38. No. 228. Dec. 1919. 3 A 



