Abstract
OBSERVATIONS OK SOLAR PROMINENCES.—A summary of the observations of prominences made at Kodaikanal during the second half of the year 1917 is given by Mr. Evershed in Bulletin No. 58. The mean daily frequency, mean height, and mean extent along the sun's limb were respectively 20.0, 37.5″, and 3.58°, differing but little from the corresponding figures for the first half of the year. There were three principal zones of activity: one about the equator, a midlatitude zone between ±30° and 40°, and a highlatitude zone between ±70° and 80°. More than half of the nineteen metallic prominences recorded were observed during December, which was also the most active month magnetically. In observations on the disc of the sun, 239 bright reversals of Hα and eighteen dark reversals of D3 were noted, and photographs of Hαabsorption markings were obtained on 117 days. The areas and numbers of the absorption markings showed a large increase on the previous half-year, indicating an increase in the density of the prominences except in the case of those occurring about latitude 60°, which have seldom given evidence of their presence on the disc. The distribution of the markings showed the usual excess on the eastern side of the central meridian.
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Our Astronomical Column . Nature 102, 97 (1918). https://doi.org/10.1038/102097a0
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DOI: https://doi.org/10.1038/102097a0