SOLAR DISTURBANCES DURING FEBRUARY. 1915. 



By FRANK C. DENNETT. 



Owing to cloud no observations were possible on five days, 

 February 2nd, 3rd, 7th, 13th, or 17th. On the remaining 

 days the disc never appeared free from spots. Spot dis- 

 turbances were more in number than in any month since 

 the autumn of 1910. The longitude of the central meridian 

 at noon on February 1st was 42 : 52 '. 



Xo. 10 of the January list remained visible until Februarv 

 6th, and therefore reappears upon our chart. 



Xo. 11. — First seen on the 4th, as a somewhat distorted 

 elliptical outbreak, thirty-nine thousand miles in length, 

 increasing until on the 6th it was fifty-six thousand miles. 

 On the 8th only a small two-umbrae spot was visible, but 

 from the 9th until the 12th, when last seen, it was a long 

 group of about eight spotlets and pores. 



Xo. 12. — On the 4th a solitary spotlet, but preceded next 

 day by pores, which on the 6th were arranged as on the 

 diagram. On the 8th and 9th a small leading spotlet with 

 a trail of tiny pores eighty-four thousand miles in length. 

 On the 10th and 11th two small spots were followed by a 

 group of pores. Last seen on the 12th. 



Xo. 13. — Two pores only seen on the morning of the 4th. 



No. 14. — A spot fifteen thousand miles in diameter, 

 just round the south-eastern limb on the 5th, having two 

 umbrae from the 8th until the 11th, and a line of three 

 pores on its northern side on the 15th and 16th. Last seen 

 on February ISth. 



Xo. 15. — A fine spot first seen well round the north- 

 eastern limb on the 8th ; on the 10th its penumbra had 

 increased to a diameter of over thirty thousand miles, 

 and in the faculae following it two pores had appeared, 

 as shown on the chart. On the 11th part of the penumbra 

 had broken off. and three pores were closely east of it, the 

 more distant ones having disappeared. Only one or two 

 pores seen near it afterwards ; last seen at the limb on the 

 20th. 



Xo. 16. — Three spotlets on the 9th, but on the 10th a 

 train of nine, as shown on the chart, sixty-three thousand 

 miles in length. The numbers were less on the 11th ; it 

 was seen until the 14th. 



No. 17. — A small spot seen from the 10th till the 12th ; 

 there was a pore twenty-five thousand miles following it. 



Xo. 18. — First seen as pores amid brilliant faculae 

 within the south-eastern limb on the 20th and 21st. A curved 

 group on the 23rd, fifty thousand miles in length. By the 

 25th the leader had grown to sixteen thousand miles in 

 diameter, and was a singular-looking object; the northern 

 trailer was also of peculiar formation ; the whole group was 



altering its appearance rapidly. It was last seen on March 

 2nd. The Astronomer Royal has kindly supplied two photo- 

 graphs of this group, taken on February 25th and 26th, 

 which are reproduced in Figures 91 and 92. Unfortunately 

 the air was not in favourable condition for photographv on 

 the 25th. 



Xo. 19. — Seen on the 21st as a close pair of spotlets. On 

 the 23rd a line of three pores close together, with a smaller 

 one following, the length of the disturbance being forty- 

 two thousand miles. Last seen next day as a solitary 

 pore in a faculic cloud. 



Xo. 20. — When first seen on the 23rd a spot ten thousand 

 miles in diameter, with a pore to the south-east, making the 

 disturbance sixty-four thousand miles in length. This pore 

 was not seen after the 27th ; but on March 2nd there were 

 three pores west and south, and on the 3rd others showed 

 south-east as well, but too small to measure The spot last 

 seen on the 5th, faculae marking the position until the limb 

 was reached on the 8th. 



No. 21. — A larger pore, followed by three much smaller 

 ones, seen on the 25th, subject to constant change. Last 

 seen on March 2nd. 



Xo. 22. — Two spotlets, bright-lipped, only seen on the 

 26th, nearing the south-western limb. 



No. 23. — A spot fifteen thousand miles in diameter, 

 just within the limb on the 26th, with fine faculae following 

 it on the 27th. On March 2nd the umbra was crossed by a 

 bright bridge. On the 7th the umbra was of the form of a 

 hook. When last seen, on the 10th it had a smaller com- 

 panion a little to the south. 



No. 24. — Two spots and two pores between them had 

 broken out close to the central meridian on the 27th. The 

 leader some ten thousand miles in diameter, and the trailer 

 afterwards marked by pores until last seen on March 2nd 

 Its length was forty-three thousand miles. 



No. 25. — A spot sixteen thousand miles in diameter 

 came round the limb on February 28th. seen to possess 

 two umbrae on March 6th, last seen on the 10th, only 

 faculae being seen in its place on the 1 1th. 



Faculae were recorded near the west limb on Februarv 

 20th ; north-west on 1st, 6th, Sth, and 24th to 26th ; 

 north-east on Sth, 16th, 18th to 20th, 24th, 27th, and 28th : 

 south-west on 4th and 10th; and south-east on 18th to 20th, 

 25th, and 26th. 



Our chart is constructed from the combined observations 

 of Messrs. John Mcll.irg. W. J. Waters, and the writer. 



DAY OF FEBRUARY, 1915. 



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B 111 



