﻿212 Mr. L. Vegard on the Properties of 



orbits of electric rays exposed to the field of an elementary 

 magnet, when applied to the sun and the earth, has also 

 shown that the main features of the aurora and magnetic 

 disturbances are simple consequences of the radiation 

 hypothesis. 



In fact I think that, all arguments collected and weighed, 

 it will hardly be possible to doubt that electric radiation from 

 the sun is the main cause of the phenomena in question. They 

 show, however, a great variety of forms and variations, and 

 further investigations will be required before we are able to 

 follow each phenomenon into details, and, above all, we have 

 al present no definite knowledge as to the physical nature 

 of those solar rays which are engaged in the production 

 of magnetic disturbances and the various forms of aurora 

 borealis. 



The determination of the nature of these rays will be of 

 great importance, not only for the study of these most 

 interesting terrestrial phenomena, but knowing the types of 

 radiations we may obtain valuable information regarding 

 the constitution of the sun. 



It is my intention in this paper to give a contribution to 

 the solution of the question regarding the physical nature of 

 the electric radiation from the sun, by trying to show that 

 certain auroral forms, especially the draperies, both as regards 

 position, occurrence, structure, and form, are explained in a 

 simple way by assuming that they are caused by a-rays, 

 or rays having essentially the same properties, while the 

 assumption of a radiation of the /5-ray type meets with great 

 difficulties. 



This a-ray hvpothesis was first announced by the writer in 

 a note to ' Mature ' *, and some further consequences have 

 been drawn in a couple of notes recently published in 

 Archiv /'. mat. og nat. Videnskab.f 



Properties of a-Pays. 



2. Before proceeding to treat the auroral problem, let us 

 first recall to our memory some of the most characteristic 

 properties of a-rays. 



The a-rays hitherto studied consist of helium atoms each 

 of which carries an electric charge 4- 2e. 



The a-rays sent out during a certain transformation pro- 

 cess will start with a quite definite velocity. As shown by 



* L. Vegard, 'Nature/ no. 2163, p. 212 (1911). 



t L. Vegard, Archiv f. mat. og nat. Videnskab.No. 6 and Xo. 9 1911). 



