PART ii. POI.AK M.\(;M.;TIC PIIKNOMK.NA AND i KURKI.I.A EXPERIMENTS. CHAP. in. 



TABLE XCV continued. 



539 



Vector diagrams of the horizontal component of S 1 * are given in fig. 197 for the four stations. The 

 vectors are drawn from points on a time-axis for every second hour. 



At Matotchkin-Schar, Kaafjord and Dyrafjord, there is an interval of several hours in the forenoon 

 with very small forces corresponding to the quiet period. At Axeloen the interval is very short. In the 

 afternoon the perturbing force increases, and assumes at each station a nearly constant direction towards 

 the north-west, which is maintained for several hoiirs. Then, all of a sudden, the perturbing force 

 turns round, takes up a direction nearly opposite to what it was in the afternoon, and assumes a com- 

 paratively large value. 



If the average storm is represented by current-arrows, we should for each station get two typical 

 current systems. 



(1) One system with maximum about six o'clock in the afternoon with its current-arrows turned 

 eastwards along the auroral zone. 



(2) A second type with its current-arrows turned westwards along the auroral zone, and with its 

 maximum about midnight. 



In the following table is given the time-interval for a small perturbing force, and the times of 

 maximum of the horizontal component of the perturbing force of the average positive and negative storms. 



TABLE XCVI. 



