Abstract
SOLAR ACTIVITY IN 1887.—The decline in the three orders of solar phenomena, spots, faculæ, and prominences which had been so marked during 1886, and particularly during the latter part of that year, continued in 1887, and although there was no spotless period so long continued as that of November 1886 (see NATURE, vol. xxxv. p. 445), the mean spotted area for the year just passed has been much below that for the year preceding it, and faculæ and prominences have shown a similar falling off. During the first four months of 1887, sunspots were both few and small, and there were several intervals of a week or longer in which no spots were seen at all; January 9-18, February 7-16, March 3-9, April 4-11, being such intervals. There was also very little on the sun from March 10-15, and from March 27 to April 18. But after this a revival set in and a fine group of spots was seen on the sun, May 14-23, appearing again in the three following rotations, June 5-18, July 3-14, and July 3O-August 9, The days of greatest spotted area during the year were July 6, 7, and 8, but after this the spots began to decrease again, and were few and small in September, October, and November. August 23. to September 12 was a very quiet period, spots only being seen on about four days; and October 6-17, October 28 to November 4, and November 21 to December 1, were spotless intervals. The last month of the year, however, showed a second rally, a fine group of spots being observed during its first fortnight, and another appearing as the first passed off at the west limb. On the whole the mean daily spotted area for 1887 was about two-fifths of that which it was for 1886. Comparing the results for 1885, 1886, and 1887, with the years preceding the last minimum, 1885 shows a somewhat greater mean daily spotted area than 1874, 1886 than 1875, and 1887 than 1876. If, therefore, the decline continues to proceed as during the last cycle, the next minimum will fall early in 1890.
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Our Astronomical Column . Nature 37, 423–424 (1888). https://doi.org/10.1038/037423a0
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DOI: https://doi.org/10.1038/037423a0