Statistics of Geomagnetic Storms and Solar Activity

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Abstract
The geomagnetic effects of Ca-flocculi and large sunspots have been investigated statistically using the method of superposed epochs. The study covers the period 1919–1954, and the main results are exhibited in a series of diagrams. Magnetic storms show a definite relation to the CMP of active regions, and the correlation is found to persist throughout the solar cycle without noticeable change of character. This applies to both recurrent and sporadic storms, but the type of correlation differs markedly in the two cases. The results lend support to the current hypothesis that there are two kinds of solar corpuscular emission: (i) prolonged emission from M-regions which are largely independent of active areas. (ii) transient emission from active areas. In both cases, the emitted particles reach the earth in an average time of 3 days. The hypothesis that the recurrent storms are caused by particle streams from active areas is shown to be untenable. M-regions tend to avoid the immediate vicinity of active areas, but are strengthened at a distance of 30°–90° from the active areas, particularly on the “following” side. The nature of M-regions is discussed in the light of the statistical evidence.

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