L96 



MAGNETIC DISTURBANCES AND AURORA. 



30, 1902. 



At 9.27 p.m. faint aurora arc from Observation V rose to a maximum at about 9.30 p.m. ; the 



Hill to Crater Hill (i.e. its centre a little south increase during the previous 3 minutes was 



of true east). Altitude 15 to 18. specially rapid, amounting to about 20y. In the 



course of about 5 minutes D increased 18' and 

 diminished 27', the turning-point answering to 

 about 9.27 p.m. Synchronous with this was a 

 sharp, but not large movement in H. 



It (aurora) had completely disappeared at 9.32 After 9.32 p.m. curves normal, 



p.m. 



The evening of June 30 was fairly quiet magnetically, but there were at about 9.15 p.m. (when there is 

 no record of aurora) sharp oscillations in D and H, very similar in character, though opposite in direction, 

 to those recorded 12 minutes later, and these were accompanied by a small but sharp temporary depression 

 in V. The general trend of V was upwards from 9.0 to 9.30 p.m., the total increment being about 65y. 



September 19, 1902. 



.Midnight (0 a.m.). Faint aurora extending I There was a large oscillation on the H curve, 

 from N.E. to S.AV. A decrease of 50y was followed by a rise of 60y. 



The turning-point was at about 0.5 a.m., the 

 double movement occupying about 50 minutes. 

 D diminished about 30' between 11.55 p.m. on 

 18th and 0.7 a.m. on the 19th. The V magnet 

 was out of action. 



The night of September 18-19 was on the whole rather quiet, but there was another oscillation in H 

 very similar to and not much less than the above, with the turning-point at about 10.50 p.m. on the 18th. 

 The observer remarks under the date September 19 that daylight was getting too bright for aurora to be 

 visible, so that the above display was presumably more than usually intense. 



May 28, 1903. 



10.45 p.m. Aurora semi-arc emanating from 

 below hill in N.W. by W. magnetic (i.e. about 5 

 north of true east) and terminating abruptly over 

 Observation Hill, N.N.W. magnetic (i.e. about 45 

 east of true south), where altitude was 20. Light 

 very faint and diffused. 



The H curve shows a marked oscillation, a 

 decrease of 45y being followed by a slightly larger 

 increase. The turning-point occurred about 

 10.47 p.m., the whole movement occupying about 

 50 minutes. 



There was no noteworthy variation in either D 

 or V, but the latter element showed a slight rise 

 after 10.55 p.m. 



May 29, 1903. 



3.0 p.m. Continued display of aurora in the S. 

 and S.E., low on horizon, from to 3 in altitude. 

 Low arcs rising close upon one another, sometimes 

 as many as parts of four or five, the southern 

 extremities only being complete. High rays 

 occasionally shot towards the zenith. The dark- 

 ness below the arcs was marked. Movement 

 chiefly from E. to S. in the rays, but from 

 3.0 to 4.30 p.m. the whole display had shifted 

 from S. to E. 



A magnetic disturbance of the special type 

 described in Chapter X was in progress. Between 

 2.45 and 3.5 p.m. D diminished 20', while H in- 

 creased a little over 40y, V remaining practically 

 constant; then in the course of the next 18 minutes 

 D increased 36', H diminished about 30y, and V 

 increased 15y. 



By 3.40 p.m. the elements had returned to 

 about the values they originally possessed and 



appeared normally quiet. 



In this instance the auroral display seems to have continued after the special magnetic disturbance had 

 ceased. 



