20 KR. BIRKELAND. M.-N. Kl. 



from a distant cathode may describe round an elementary magnet. But 

 as long as the distribution of all paths in space is not found, and as long 

 as the analysis gives no information as to how the corpuscular rays really 

 group themselves together in crowds round the elementary magnet, the 

 utility of the solution is very limited. It fails even in an endeavour to 

 explain the very simple but important phenomena of positive and negative 

 polar magnetic storms. 



Let us now consider the reasons why Størmer believes that he is 

 authorized to tell us, that the rays in an auroral curtain are produced by 

 positive corpuscle rays. He has studied a single magnetogram from the 

 Haldde Observatory corresponding to the time, when he photographed 

 an auroral curtain. 



The magnetogram shows a positive polar magnetic storm at the time 

 of Størmer's observation, and this positive polar storm is superposed on 

 a much larger negative storm. Stormer does not mention these two 

 storms: he only presupposes that the magnetic dellection corresponding to 

 the positive storm is produced by the observed auroral rays. 



But the deflection corresponding to the simultaneously existing much 

 greater negative storms are simply disregarded. 



It is easy to demonstrate that it is dangerous in this matter to draw 

 far-reaching conclusions from a single magnetogram. I have examined 

 twenty four hundred curves, so I have more experience. Not all obser- 

 vations can be made in a few weeks like the photographing of auroras. 

 If we study magnetograrns from somewhere in the lower part of the 

 auroral zone, we find that there exist great positive polar storms at times 

 when no north-light curtains can be observed, and there also occur great 

 negative magnetic storms when no auroral drapery appears. 



But almost always when the two storms overlap or are superposed 

 on one another, and when the two storms directly succeed one another 

 so that at this time the magnetic deflections frequently change direction, 

 auroral curtains are found to exist simultaneously. In the present case it 

 is obvious that Professor Stormer has not taken into account the domi- 

 nating features of the phenomenon he studies, as he has not considered 

 the existing magnetic positive and negative polar storms. 



In my work »Aurora Polaris« almost all researches were made with 

 the purpose of finding the cause of such magnetic storms. 



I find that during the negative polar storms with maximum on the 

 night-side of the earth, the helio-cathode rays are precipitated down towards 

 the aurozal zone, whence on an average they bend eastwards before they 

 set out into space again. 



