Magnetic Storms

Abstract

EXACTLY twenty-seven days from the magnetic storm and splendid aurora of February 13–14, which has already been mentioned in NATURE, there was on March 12 another very fine aurora in the United States and Canada, and it also was accompanied by a powerful magnetic storm. This correspondence to the time of a synodic revolution of the sun, to which attention has been called by the writer many times within a few years past, is interesting, showing as it does that the motion of rotation is concerned to an important extent in the recurrence of magnetic storms and their accompanying auroras. The evidence is accumulating constantly showing that solar disturbances have their maximum effect upon terrestrial magnetism when at the eastern limb and at or near the latitude of the plane of the earth's orbit. If the great sun-spot to which the aurora of February 13 has so generally been ascribed was really responsible for that outbreak, there should have been a series of displays, for this spot was very large and apparently active throughout its transit. As a matter of fact, whatever auroral effect the disturbed region in its vicinity was able to exercise fell about February 2–4 and February 29. Upon the latter date there was a fine display, but upon the former it was generally cloudy.