Geomagnetic solar flare effect in the dark hemisphere

Abstract

Normal run magnetogram data obtained at Huancayo, Kodaikanal and Kakioka show that the geomagnetic solar flare effect (SFE or Crochet) occurs not only in the sunlit hemisphere but also in the dark hemisphere. Using a selected sample of five events observed over the period from 1969 to 1971, it is found that a discrepancy exists between the observed characteristics of nighttime geomagnetic SFE and those expected from the interpretation that the nighttime geomagnetic SFE is due to induced currents that are forced to flow into the dark hemisphere owing to the sudden increase in electrical conductivity of the sunlit hemisphere. This discrepancy may be due to some of the inherent assumptions of the theoretical model used for calculating the characteristics of induced currents in the dark hemisphere.