Recent Auroræ and Magnetic Disturbances

Abstract

WITH reference to the displays of aurora on January 7 and February 3, reported in NATURE of February 13 and 20, pp. 277 and 318, the following further details may be of interest. The aurora of January 7 was noted by an observer in the vicinity of Preston, who reported seeing it between 19h. and 191½h. U.T. On this occasion, the magnetic records of Stony hurst Observatory show a moderate disturbance between 18h. and midnight, the most notable movements being a fall of 27 in westerly declination between 19h. 15m. and 19h. 32m., followed by a sharp rise of 28 between 19h. 32m. and 19h. 42m., whilst horizontal force rose by 140 between 19h. 22m. and 19h. 34m. and then fell by 180 between 19h. 36m. and 19h. 43m. It may be noted that on this occasion the minimum value of D almost coincided with the maximum value of H. On February 3, however, these conditions were reversed, the minima in D and H being almost, but not quite, coincident in time. On this occasion, declination fell by 70 between 18h. 58m. and 19h. 12m., whilst horizontal force fell by 225 between 18h. 56m. and 19h. 09m., each element rising by corresponding amounts in the next ten minutes.