The Great Sun-spot Group and Magnetic Disturbances, May 8–21


ON May 8 there appeared on the sun's eastern limb an equatorial sun-spot in a region which has been without disturbance for some considerable time. It was an active spot which had separated by May 12 into two large spots. The maximum area of the group was 16.5, in units 1/5000 of the sun's visible disc, and this was attained on May 14. The leader spot of the group was a composite spot containing two umbræ. Its mean heliographic co-ordinates on that date were latitude +1.4°, longitude 6.4°. The following spot was a large single spot, and its co-ordinates were latitude 0.2°, longitude 358.8°. The whole group extended over 12° in longitude and about 6° in latitude, so that a considerable area of the sun's surface was disturbed.

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CORTIE, A. The Great Sun-spot Group and Magnetic Disturbances, May 8–21. Nature 107, 426–427 (1921).

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