PART II. POLAR MAC.NKTIC PHKNOMKXA AND TF.URELLA EXPKKIMKNTS. CHAP. II. 441 



which SreRMKR has found by calculation. The rays answering to values of y between 0.3 and 0.9, are 

 specially noticeable. 



In reality, the constitution of the current-system which produces the magnetic storms of this type, 

 is rather complicated, as there are at the same time perturbations in the north, which cannot be ex- 

 plained merely by an equatorial current-system. This is in perfect accordance with the conditions of 

 which the experiments give a hint. Fig. 38, a and b, gives, for instance, quite distinct information of 

 the existence of a connection between the rays which operate in the equatorial regions at a distance 

 from the earth, and those which come in a wedge close in to the earth in the polar regions, the latter, 

 in our opinion, being the cause of aurora polaris and the polar magnetic storms. 



The patch of light in the polar regions, seen in fig. 37, is, we believe, connected with the powerful 

 and strictly local storm in Kingua Fjord, which we found during the perturbation of the i5th December, 1882. 



Similar polar precipitation, of which the existence cannot be so directly proved, should, we believe, 

 be regarded as the cause of a number of apparently abnormal conditions that we found, for instance, 

 in the perturbations of the 26th January, 1903 (p. 67), the 22nd March (p. 128), and the 24th November, 

 1902 (pp. 273 & 274!. 



The serrations that we find most strongly marked in the polar regions, must similarly be ascribed 

 to polar precipitation. Simultaniously with the change in the equatorial current-system which produces 

 the various serrations in the curve, slight polar precipitation will occur at places in the polar regions, 

 acting locally with comparative power, but its effect decreasing rapidly outwards. 



These occurrances of slight polar precipitation will always accompany a positive equatorial storm. 

 For this reason, the character of the curves in the polar regions is very irregular in comparison with 

 those farther south. This may be seen, for instance, by comparing Axeleen with Bombay or Batavia 

 'ii PI. XIV. We must thus, during the positive equatorial storms, imagine a constantly acting, more 

 itorial current-system, and a number of slight occurrence of polar precipitation in the north and south. 

 As these two systems are undoubtedly, as we have said, connected with onea nother, a change in the one 

 will always or at any rate as a rule be accompanied by a corresponding change in the other. We 

 shall demonstrate this more clearly later on in the experiments, which show that the rays may run for 

 a time more or less in the magnetic equator, but then intersect that plane at continually increasing 

 angles, after which they finally descend in polar regions. 



We next have the polar magnetic storms. In these, the most powerful forces are found in the 

 polar regions, while the forces decrease very rapidly in strength with descent to lower latitudes. 



In these storms, it will be possible, as a rule, to demonstrate in the polar regions one or more 

 more or less distinctly defined areas, within which the most powerful perturbing forces are gathered. It 

 appears that as a rule the character of the storm is mainly dependent on whether, in this area, there are 

 positive or negative deflections in horizontal intensity. When the former occur, we disignate the storm 

 as a positive polar storm, when the latter, a negative. 



We will first look at the negative polar storm. It occurs very frequently, and often attains a very 

 considerable strength. In order to obtain an insight into the nature of the storm, we looked out the 

 vi.ry simplest of those contained in our material, and these were first discussed. 



Among the chief peculiarities of the negative polar storm, it may be pointed out, in addition to 

 that already mentioned, that the character of the curve in the polar regions is generally much serrated 

 and irregular, which indicates that the acting forces, or current-systems, as we prefer to call them, must 

 approach comparatively near to the place under consideration, coming nearest to the earth, now in one 

 place, now in another. In lower latitudes, on the other hand, this disturbed character disappears, and 

 the course of the curves is fairly even and quiet, although considerable deflections occur. 



