Heliolatitudinal Distribution and Hemispheric Asymmetry of Source Locations for Super Geomagnetic Storms (Dst ≤−250 nT) During Different Phases of Solar Cycles

Abstract

We studied the heliolatitudinal distribution and hemispheric asymmetry of source locations for super geomagnetic storms (SGSs) (Dst \(\leq -250\) nT) during the ascending phase, solar maximum, descending phase, and solar minimum. The proportions of SGSs during the ascending phase, solar maximum, descending phase, and solar minimum were 16.1%, 33.9%, 48.2% and 1.8%, respectively. For SGSs with source locations in the heliolatitude above 20° in both hemispheres, the proportions during the ascending phase, solar maximum, descending phase, and solar minimum were 50%, 26.3%, 31.2%, and 0%, respectively. For SGSs with source locations within the heliolatitude range of [11°, 20°] in both hemispheres, the proportions during these phases were 50%, 52.6%, 43.8%, and 100%, respectively. For SGSs with source locations within the heliolatitude range of [0°, 10°] in both hemispheres, the proportions during these phases were 0%, 21.1%, 25%, and 0%, respectively. For all SGSs, the N–S asymmetry was significant over the period from 1932 to 2024. Specifically, during the ascending phase, solar maximum, and descending phase, the N–S asymmetries were significant, marginally significant, and not significant, respectively. Throughout these periods, the source locations of the SGSs were consistently dominated by the northern hemisphere. For all SGSs, the E–W asymmetry was insignificant over the period from 1932 to 2024. Specifically, during the ascending phase, the E–W asymmetry remained insignificant. In contrast, during the solar maximum, the E–W asymmetry became significant, with SGS source locations predominantly in the western hemisphere and an anti-correlation observed between the number of SGSs in the two hemispheres. During the descending phase, the E–W asymmetry was significant once again, but this time with SGS source locations dominated in the eastern hemisphere, maintaining the anti-correlation between the two hemispheres. Only one SGS was observed during the solar minimum, with a source location at S11W21.