SOLAR DISTURBANCES DURING APRIL, igi5- 



By FRANK C. DENNETT. 



The Sun was under observation every day during April, 

 and spots were always visible, with the exception of the 

 17th, when only faculae were present. The longitude of 

 the central meridian was 345° 30' at noon on April 1st. 



Nos. 34, 35, and 37 of the March list continued visible 

 until April 2nd, 4th, and I Ith respectively, and therefore 

 reappear upon the present chart. 



No. 39. — First seen on April 2nd as a group of pores, 

 the largest leading, about two days round the limb. The 

 leader increased to eleven thousand miles in diameter, 

 and its appearance, as also the disposition of the pores, 

 was subject to constant alteration. The length of the group 

 was seventy thousand miles, and it was last seen close to 

 the limb on the 12th. 



No. 40. — Seen close to the limb as a spot on the 2nd, 

 Pores extended away behind for fifty-five thousand miles 

 on the 4th, but increased to ninety-eight thousand miles. 

 The leader also increased in size to fifteen thousand miles ; 

 then broke up into smaller spots Last seen at the limb 

 on the 13th. 



No. 41. — A pore in a bed of faculae, only seen on the 10th. 



No, 42. — A pair of pores, forty thousand miles apart, in 

 the south-eastern quadrant, two or three days from the 

 limb ; seen on the 12th and the 13th. The place was 

 marked by faculae on the lOth, 21st, and 22nd 



No. 43 — A group of pores in northern latitude, near the 

 central meridian, twenty-two thousand miles in length, 

 visible from th- 13th until the 15th. 



No. 44. — Two spotlets, some thirty-four thousand miles 

 apart, had broken out in a faculic bed near the south- 

 western limb on the 15th, one remaining visible until the 

 next day. 



No. 45. — .\ pore, only seen on the 18th, in north latitude, 

 some 17° past the central meridian. 



No. 46. — First seen as a pore on the 18th, but on the 

 19th as a group of five. On the 21st two small spots with 

 six pores between them. From the 22nd until the 24th 

 the trailer was only a pore. The greatest length of the group 

 was fiftv-two thousand miles, and the leader was last seen 

 on the 27th. 



No. 46i7. — .\ small spot with pores, south-west of the last, 

 first seen on the 20th. On the 21st two spots with pores 

 between, Th" trailer afterwards broke up into pores, but 

 the leader increased to fifteen thousand miles in diameter, 

 the group being sixty-four thousand miles in length. On 

 the 26th onlv one pore seen behind the leader, and on the 

 27th and the 28th the spot was seen alone ; on the later 

 day ven»- close to the limb. 



No. 46fc. — A spotlet and pore only seen on the 22nd, 



No. 47.- — A solitary pore in the north-western quadrant, 

 only seen on the 19th, 



No. 48.- — A pore in a faculic area in the south-eastern 

 quadrant, seen on the 19th and the 2Uth. 



No. 49. — A pore, only seen on the 21st, 



No. 50. — A spot with two small companions appeared 

 close to the south-eastern limb on the 26th, The spot became 

 thirteen thousand miles in diamel'^r, and on the 28th and the 

 29th its penumbra was blotted out by pliotospheric matter 

 on the preceding side. On May 2nd its umbra was become 

 double, and on the 6th a bright bridge cut the spot into two. 

 It was last seen at the limb on the 8th. The pores following 

 it were subject to constant change, a conspicuous one showed 

 some 8° south-east on .\pril 28th, the distance increasing 

 to seventy-seven thousand miles. This last remained visible 

 until the morning of May 6th, none others being seen 

 after the 2nd, 



No. 51 (see Figure 167) is a return 

 of the great group No. 37. The large 

 spot was first seen on the 26th. The 

 remaining portions of the group became 

 more clearly visible as they advanced 

 farther on the disc. The large spot 

 dwindled as it crossed the disc, its dia- 

 meter was some eighteen thousand 

 miles across, and it was last seen on 

 May 8th. The group of pores west of the large spot were all 

 gone after May 5th. On the 2nd and the 3rd a group of pores 

 was seen directly south of the large spot. Spotlets a little 

 south-east of the large spot, seen first on .\pril 27th, remained 

 visible, but much altered, until May 5th, The trailer group, 

 first seen on April 28th, was protean in appearance, but 

 continued visible until May 6th, This group of groups had 

 a length of one hundred and seventy thousand miles. To 

 prevent confusion a small chart of this group is given. 



No. 52. — A spot first seen on April 28th, with a diameter 

 of nine thousand miles. It was last seen as a pore, nearing 

 the limb, on May 9th. Possibly a return of No. 39. 



No, 53. — A spot ten thousand miles in diameter, with a 

 small attendant on April 30th. It was a small group 

 until May 4th ; afterwards a spotlet with a pore fifty 

 thousand miles in its rear. From the 8th until the 10th, 

 when it was last seen, the spotlet was solitary. 



No. 54. — A group of five pores sixty-three thousand 

 miles in length, only seen on April 30th. 



Our chart is constructed from the joint observations 

 of Messrs, J. McHarg, E. E. Peacock, W. J. Waters, 

 R, Marchment, and F. C. Dennett. 



vo ao so SK jio 

 Figure 167. 



DAY OF APRIL, 1915. 



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