Abstract
ON May 10·4 a large sunspot, crossing the sun's disk between May 4 and 17, reached the central meridian. The sunspot had originated on the sun's invisible hemisphere, and it seemed of possible significance that the longitude of the spot, 189°, differed little more than 10° from that of the large and spectroscopically active spot associated with the great magnetic storm of April 16 (NATURE, April 23, p. 721). On May 11 at 15h 52m U.T. a magnetic disturbance began, and this developed within a few hours into a "great"magnetic storm which, reaching a maximum towards Oh (May 12), was accompanied by a display of the aurora borealis. At Greenwich the aurora was first seen by chance at 23h 48m U.T. by two of the astronomical observers, though from other reports it must have appeared some minutes before this time. The aurora, which was bright and of a deepish red colour, was described as having the form of a fan-shaped bundle of rays the apex of which extended to about 10° south of the zenith ; at Oh 10m only faint streamers were visible. Since there was bright moonlight at the time, this aurora must have been intrinsically a very bright one, and doubtless other features would have been seen had the sky been dark. The records from the Greenwich magnetic station at Abinger, kindly communicated by the Astronomer Royal, give the following (provisional) ranges: in Declination, 80' ; in Horizontal Force, 960 γ ; and in Vertical Force, 420 γ. There was considerable ionospheric disturbance affecting long-distance short-wave radio transmission during the period of magnetic disturbance.
Article PDF
Rights and permissions
About this article
Cite this article
Sunspot, Magnetic Storm and Aurora on May II. Nature 141, 930 (1938). https://doi.org/10.1038/141930c0
Issue Date:
DOI: https://doi.org/10.1038/141930c0