A Possibility of Modulating the Geomagnetic Field by the Solar Eclipse

The solar eclipse affects terrestrial environments in various aspects. For instance, it is well known that the electron concentration and current density decrease in the ionosphere due to the reduction of solar irradiation during solar eclipse. In this study, we carry out the statistical analysis of x, y, z, H-components, and the intensity of the geomagnetic field using the ground based geomagnetic data observed during the solar eclipses from 1991 to 2016. First, we confirm that characteristic decreases in the x and H-components can be seen in the vicinity of the maximum eclipse time at the observing site. Second, we find that the decrease in x and H-components is more conspicuous during the total solar eclipse rather than the partial or annular eclipses. We also find that such a dip is likely to be noticed when the observing site locates in the second half compared to the first half of the eclipse path, as well as when the eclipse occurs in dusk side than in dawn side. Third, we find that reductions in the ground geomagnetic field by the solar eclipse are more evident in the ascending phase of the solar cycle than in the descending phase. Finally, we briefly discuss implications of our findings.