The Magnetic Storm of April 16

Abstract

THE magnetic storm which occurred during the Easter week-end appears to have been one of the most violent ever recorded. Particulars of the disturbance have been supplied to NATURE from the Abinger magnetic station of the Royal Observatory, Greenwich, and from Edinburgh. The storm, as recorded at Abinger, considerably exceeded that of January 25 of this year both in range and in intensity. At intervals the photographic traces are difficult to follow on account of the rapidity of change in the earth's magnetic field. Beginning at 5 h. 48 m. U.T. with a sudden sweep of 45' in declination, the storm almost immediately attained dimensions sufficient to place it among the “great” storms of the past hundred years. Only the salient features are at present available. These may be summarized as follows: The period of most intense activity was from 6 h. to 8 h. U.T. and the storm had virtually ceased by 16½ h. The whole range in the vertical component of the field was approximately 500 γ— not very remarkable except for the short interval of fifteen minutes during which it occurred—between 7 h. 35 m. and 7 h. 50 m. The ranges in declination and horizontal intensity are at present subject to reservation. On account of the rapidity of change some doubt exists as to the identification of the auxiliary traces which are brought into the record in lieu of the displaced ordinary trace when large ranges occur. A tentative estimate of 5° in declination and 2250 γ in horizontal intensity (that is, nearly one eighth of the whole) has been made by the assistant in charge of the Abinger station.