A Big Sunspot

    Abstract

    A BIG sunspot has crossed the solar disk during the past week; appearing at the east limb on March 20, reaching the central meridian on March 26–3 and due to pass around the west limb of the disk on April 1. The area of the spot on March 23 was 1,000 millionths of the sun's hemisphere—an area well above the lower limit of size for naked-eye visibility. On March 23, a bright chromospheric eruption of considerable intensity was observed directly over the spot. A great magnetic storm began on March 23 and was in progress during the night of March 24–25, when the aurora was also seen in spite of bright moonlight. Widespread interference with both radio and cable communications was reported.

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    A Big Sunspot. Nature 145, 509 (1940). https://doi.org/10.1038/145509c0

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