Institution(s): 1. University of Nigeria
The variation in the Earth’s magnetic field associated with X class solar flares have been studied. Thirty (30) most powerful X-class solar flares that occurred between 1976 and the end of the last solar cycle have been investigated with a view to understanding the effect of this class of flares on the geomagnetic field. The geomagnetic solar flare effect (sfe) associated with these solar flares, as observed in fifteen geomagnetic station with data resolution of minutes have been computed. We obtained a good correlation (r >0.73) between the normalized H component amplitude of the solar flare effect (Hsfe) and the intensity of the solar flare especially for the solar flares that occurred within 45o of the central meridian of the solar disk at. Stations within the mid latitude generally showed better correlation than those at higher latitudes. The Z component amplitude of the solar flare effect (Zsfe) generally showed weaker correlation (r>4.6) with the solar flare intensity, and this correlation was better for high latitude stations. The results from this study have important implications for our present understanding of the nature of- and complexities in- the ionizations that lead to the geomagnetic solar flare effect.