SOLAR DISTURBANCES DURING DECEMBER, 1912. 



By FRANK C. DENNETT. 



December was very cloudy, and hence the record is some- 

 what imperfect, no less than eleven days having been missed 

 completely. On six days (2, 3, 8, 9, 10, and 28), the disc 

 was apparently free from disturbance, and on one, the 23rd, 

 only faculae were seen, spots being visible on the remaining 

 thirteen. The longitude of the central meridian at noon on 

 December the 1st, was 54° 36 . 



No. 24. — First seen in a faculic disturbance a little way on 

 the disc from the eastern limb on the 12th, a spot with tiny 

 pores, some before and some behind it. On the 16th it 

 showed two distinct umbrae. The larger spot had seemingly 



length, seen on December the 17th, only one of which, the 

 leader, was found next day. Its place was marked on the 

 20th by a faculic area. 



No. 26.— A group of spotlets and pores, 46,000 miles in 

 length, first seen on the 29th, which changed its appearance 

 considerably during its visibility, being last seen amid faculae 

 close to the north-western limb on January 3rd. 



During the past year only 27 outbreaks of spots have been 

 recorded, one being of a secondary character. Of these. 22 

 have appeared in the southern hemisphere, and only five in 

 the northern. It is somewhat singular that in December, 1911, 



DAY OF DECEMBER, 191 2. 



30 40 SO 60 70 



so m no a 130 ho 150 m 170 iso bo 



IB 210 230 2*0 250 260 270 



790 300 310 320 330 340 350 360 



broken into two next day, and on the 18th was much less 

 conspicuous, not being seen after. 



No. 24fl. — This disturbance, certainly connected with the 

 last, appeared some 50,000 miles in front of it, on the 16th — 

 if not on the 15th — a spot with some pores round. On the 

 17th two dark penumbral spots had developed almost midway 

 between the southern components. On the 18th the rear spot 

 of this group had formed, nearly equal to the leader. On the 

 20th, both these spots were still visible, but on the 22nd only 

 the leader remained amongst a quantity of faculic matter, 

 whilst this spot was not to be seen on the 23rd, only the 

 faculic remains of the outbreak. The length of No. 24 was 

 30,000 miles, a. 45,000, and the double group 82,000 miles. 



No. 25. — A group of spotlets and pores, 35,000 miles in 



a little disturbance broke out in 23° N. Latitude, and now 

 again in December, two disturbances have made themselves 

 visible, one in 17°, the other in 27° N. Latitude. These may 

 prove to be the forerunners of a new cycle of solar phenomena. 

 The second chart shows the distribution of the spot distur- 

 bances during the year. The collection of disturbances into 

 groups is again a noticeable feature in the southern hemisphere. 

 One chain of activity extends from 350° to 82°, and another 

 from 153° to 220°, and a third from 228° to 330°, many of the 

 second group drawing very near the equator. Of the 53i days 

 upon which the Sun has been observed, spots were recorded 

 on 108, faculae were seen on 99, whilst on the remaining 126 

 the disc presented an unruffled surface. 



Our monthly chart is from the combined observations of 

 Messrs. J. McHarg, A. A. Buss, E. E. Peacock, W. H. Izzard, 

 and the writer. 



DISTRIBUTION OF SPOT-DISTURBANCES DURING 1912. 



» 20 JO tt 50 60 



80 90 100 IB 120 ISO 140 150 160 170 



200 210 220 230 2(0 ZSO 30 IV mi 290 300 310 $20 130 340 350 360 



69 



