Abstract
A RECENT group of sunspots, not remarkable for size, complexity or visible changes of structure, has proved of interest on account of its great activity when observed spectroscopically, especially in the hydrogen line C or Ha. of the solar spectrum. The group consisted of two spots of regular outline, 10° apart in solar longitude, accompanied by two or three wide clusters of small spots, making in all a stream extending over 20° of longitude. The position of the centre of the stream was: long. 164°; lat. 27° S.; central meridian passage February 14-0, when the spots passed about 20° of latitude south of the centre of the sun's disk. The area of the stream averaged about 800 millionths of the sun's hemisphere or 930 million square miles. Between February 7 and 14 inclusive, the spots were examined as often as possible with the Hale spectrohelioscope at the Royal Observatory, Greenwich, for a total duration of 16 hours on six days, usually before 13h U.T. During these hours of watching, equivalent to about one-ninth of the total duration of the epoch, eight bright eruptions of hydrogen were observed, so that a considerable number of eruptions is indicated by this sampling as having taken place in connexion with the spots.
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An Active Group of Sunspots. Nature 137, 311–312 (1936). https://doi.org/10.1038/137311d0
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DOI: https://doi.org/10.1038/137311d0