The Magnetic Storm of March 22–23 and Associated Phenomena

Abstract

A VIOLENT magnetic storm occurred on March 22–23. It had an S.C. (“sudden commencement”) about 9h. 10m. on March 22. This was not outstanding, except that the initial increase in H was immediately followed by a reverse movement, bringing the element below its normal value for the next two hours. The normal value was sensibly exceeded from 12½h. to 14h., and again most of the time from 16½h. to 19h. The maximum occurred just after 17h. In the course of twenty-five minutes, from about 16h. 50m. to 17h. 15m., H rose 280γ and fell 360γ. The trace was off the sheet on the negative side for about six minutes near 1h., eight minutes near 1h. 30m., and thirteen minutes shortly after 4h. It was rising rapidly after each reappearance, so that the range shown on the trace, 810γ, was probably considerably exceeded. The largest movements were from 16½h. to 19h. on March 22, and from 0h. to 6h. on March 23. There was a comparatively quiet interlude from 19½h. to 23h. on March 22. The times of greatest disturbance in declination synchronised fairly with those in H. The extreme westerly position was recorded about 17h. 8m. on March 22, and the extreme easterly position near 1h. 40m. on March 23, when the trace was off the sheet for twelve minutes. There were several exceptionally large rapid movements. In the course of about five minutes from 17h. 8m. to 17h. 13m. there was a swing of 1° 35′ to the east, immediately following a somewhat less rapid swing of 44′ to the west. In the course of about twelve minutes from 1h. 9m. to 1h. 21m. on March 23 there were swings of 76′ to west and 59′ to east, and after a minute's pause the latter swing continued, so that declination at 1h. 28m., when the trace went off the sheet, was 1° 35′ less westerly than it had been nine minutes before. The range actually shown on the sheet, 2° 1′, has seldom been equalled at Kew, and as the trace was off the sheet for twelve minutes it was probably sensibly exceeded.