Relations between geomagnetic activity and major (importance > 2 + ) solar flares are studied, with primary attention to magnetic type and location of the flaring sunspot group. The data cover the years 1937-1959 and include 580 observed major flares. It is found that a major flare occurring in association with a magnetically complex (y or Py) sunspot group is much more likely to be followed by a major geomagnetic storm than is a similar flare in a unipolar (a) or bipolar (/3) group.

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... flares show the expected concentration toward the central regions of the solar disc, and also an unexpected concentration in the northern solar hemisphere. In the 23 years studied, northern spot groups produced 62 percent of all observed major flares, and 86 percent of those followed within 3 days by a great geomagnetic storm. This north predominance of great-storm flares appears about equally in each of the three sunspot maxima covered and is apparently not related to the 11-year or 12-year solar cycles.