212 



BIRKELAND. THE NORWEGIAN AURORA POLARIS EXPEDITION, IQO2 1903. 



TABLE XXXII. 



This storm, as the table and the curves show, appears to be a system tha.t occurs simultaneously 

 at all the places at which it is in any degree observable, and has more or less the same course. The 

 effect of the force diminishes on the whole, with increasing distance from the district surrounding the 

 Norwegian stations. This storm must therefore be classed with the polar elementary storms, and as one 

 of the very simplest. 



The properties of the field may be briefly characterised by saying that its form is typical of the 

 polar elementary storms that have their storm-centre about the Norwegian stations. It commences also 

 at the usual time of day. In this way we find again the following typical properties: 



(1) An area of convergence situated in the regions about Europe and western Asia. 



(2) The point of convergence moves eastwards. 



(3) An area of divergence in North America. 



On the charts VIII and IX the hours 22 h and 22'' 20, the point of convergence is in the regions 

 north of Pawlowsk. P t is comparatively small, and P, is directed upwards. In the later charts, the 

 forces show that the point of convergence has moved towards the east, the arrow having turned with 

 the hands of a clock. The current-arrows at the Norwegian stations are directed westwards along the 

 auroral zone. At Kaafjord and Matotchkin Schar, P, is directed upwards, and at Axeleen downwards, 

 showing that the horizontal portion of the current passes to the north of the two former stations, but to 

 the south of the latter. 



