Further Evidence Regarding the Correlation between Solar Activity and Atmospheric Electricity

THE geophysical element which has thus far shown -L the most marked correlation between manifestations of solar activity, as, for example, sunspotted-ness and prominences, is some measure of activity of the earth's magnetism. The range of the magnetic diurnal variation, as shown by observations extending over nearly a century, is known to pass through a definite fluctuation to the extent of 50 per cent., or more, during a sunspot cycle. The synchronism between the solar curve and the magnetic curve is not exact, however, the times of maxima of the two curves differing not infrequently by one year or more. Thus, at the Kew Observatory the absolute daily range of the magnetic declination during the period 1858-1900, or approximately 4 sunspot cycles, passed through a maximum value, three times out of the four cases, one year in advance of the sunspot maximum. During the recent sunspot cycle (1913-1923) the maximum magnetic activity showed a lag of two years with reference to the solar curve. In 1893, when sunspottedness was a maximum, the earth's magnetic activity, after having been increasing for several years previous, was quite markedly lessened, and then rose to a maximum value in 1894.