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BIRKELAND. THE NORWEGIAN AURORA POLARIS EXPEDITION, igO2 1903. 



cease as far as Kew is concerned. Here, on account of the intermediate storms, the perturbing force 

 thus becomes at the moment when the storm is at its height. During the brief storm, the current- 

 arrows are directed ESE, and these should be connected with the brief, powerful storm at Axeleen, just 

 as the latter is naturally connected with the powerful impulse in the southern Asiatic district. 



The assumption that a distant system such as that in the vicinity of Sitka would have so great an 

 effect in Europe as we find here, may, however, present some difficulty; and yet more doubtful does 

 such an explanation become when we look at the conditions at Kaafjord, where, all through, a system 

 is acting which produces current-arrows with an easterly direction. Simultaneously with the intermediate 

 storm at Axeleen, there appears to be an intermediate storm here, which, as far as H is concerned, 

 begins, reaches its maximum, and ends, almost at the same times as the storm at Axeleen. The deflec- 

 tions, however, are the reverse of those at Axeleen, as in this case we find positive values of PI, , and 

 the strength is considerably less. In the declination, on the other hand, there is a rather brief impulse in 

 an easterly direction, with maximum at about 13'' 30"', being therefore almost exactly simultaneous with 

 the maximum of the first deflection at Wilhelmshaven. The curves at Matotchkin Schar show in some 

 respects a resemblance to the conditions at Axeleen, and in others to those at Kaafjord. In H the maximal 

 negative deflection occurs earlier than at Axeleen, and about simultaneously with that in the declination at 

 Kaafjord, i. e. at about I3 h 30, while at the same time there is also a fairly powerful easterly deflection 

 in the declination. As regards the intermediate storm, the conditions at Matotchkin Schar might seem 

 to form a connection between the conditions at Axeleen and those at Sitka, thus indicating that we had 

 before us a connected intermediate system with current-arrows on the night-side of the earth directed 

 westwards. If we accept the first explanation of the conditions, we should thus have to ignore completely 

 the effects of the system in the neighbourhood of Kaafjord, a system which seems, indeed, to be compara- 

 tively weaker, and in that respect will have a more limited sphere of action, but on the other hand is 

 so close to the Central European stations, that its effect there will in all probability be very apparent. 



It should be remarked that the effect in Central Europe of this system in the neighbourhood of 

 Kaafjord is similar to that of the assumed system at Sitka, as they will both produce current-arrows 

 directed westwards. 



Finnally, as the conditions at Matotchkin Schar appear to indicate that the system at Sitka is con- 

 tinued westwards to Axeleen a circumstance that we have previously continually met with there is 

 every probability that the westward-directed intermediate current-arrows are the effect of the system 

 observed at Kaafjord. Farther west we should without doubt have found this system more fully deve- 

 loped; and observations from Dyrafjord would therefore have been of great importance here. 



We must suppose then that the effect of the southern system near Kaafjord might first predominate, 

 then the stronger but more distant system near Axeleen at the time when the latter is at its height, and 

 finally the southern system once more. The fact that the conditions in the Asiatic districts are more 

 analogous to those at Axeleen also finds a natural explanation here, the southern system at Kaafjord 

 being of far less strength than that at Axeleen, and therefore having a correspondingly smaller area 

 of action. We are confirmed in these assumptions by the course of the broken-lined arrows in 

 Charts IX and X. Thus on Chart IX we find an indication of a small area of divergence on the day- 

 side, and a larger area of convergence on the night-side; while on Chart X this area of convergence 

 extends farther west to the western stations of Central Europe. 



The storm at Axeleen is an afternoon storm, and ought therefore to be compared throughout with 

 such storms, e. g. those of the I5th and 8th February, 1903, and the 2yth October, 1902, where we 

 also found two rather different systems acting at Axeleen and at Kaafjord. 



The last great intermediate storm, from n 1 ' i2 m to o 1 ' 42 m , has on the whole been already charac- 

 terised, as we have previously proved that it has the same field of force as the ordinary polar elementary 

 storms that occur about midnight, and have their centre about the Norwegian stations. 



