and Nature of the Cosmic Electric Rays, 63 



changes of: luminosity distribution from variations of the 

 properties of the cosmic rays. 



The essential features of the change o£ luminosity distri- 

 bution must under the conditions present be produced in the 

 atmosphere even when the rays are homogeneous. 



Changes of the upper strata of atmosphere which could 

 produce the observed changes of luminosity distribution are 

 excluded only for the reason that the most different lumi- 

 nosity distributions may follow in rapid succession or even 

 simultaneously. 



Rays which are observed at different heights in the atmo- 

 sphere might give a different luminosity distribution even 

 when the cosmic rays were of the same nature and only 

 differed with regard to velocity and penetrating power. 

 Variations caused in that way probably exist, but they 

 cannot explain the essential features of the great variations 

 of luminosity which we observe, for these variations are 

 found for aurorse which have their bottom edge at the very 

 same height. 



As in a space free from forces a homogeneous ray bundle 

 should produce a definite luminosity distribution, we must 

 therefore assume that changes of luminosity distribution 

 must result from the effect of magnetic or electric fields of 

 force, or the law of absorption of the cosmic rays in the atmo- 

 sphere must be greatly influenced by fields of force. 



Any constant electric field cannot alone produce lumi- 

 nosity variations of the type here found, and even a variable 

 electric field cannot alone produce the observed effect. 

 Such a field might cause a deflexion of the ray bundle, but 

 these deflexions are small because the auroral ray streamers 

 always follow nearly the magnetic lines of force. 



The cosmic rays might be retarded or accelerated by the 

 electric field from the earth; this would mean some change 

 of velocity of the rays, and a corresponding change of 

 penetrating power, but any essential change of the light 

 distribution curve cannot be produced in that way, ami 

 further we have seen that the changes of luminosity may 

 occur without change of height of the bottom edge. It then 

 remains to consider the possible effect of magnetic fields. 



As mentioned in the paper read before the Geophysical 

 Congress at Gottenburg, the type of variation shown by the 

 luminosity as well as the smaller height of the bottom edge 

 of the ray-form can be explained in a simple way as an effect 

 of the permanent magnetic field of the earth. 



When the electric rays move in a uniform magnetic field 

 parallel to the magnetic lines of force, they will keep on 



