Local Time and Hemispheric Asymmetries of Field-Aligned Currents and Polar Electrojet During May 2024 Superstorm Periods

Abstract

This study examines field-aligned currents (FACs) and polar electrojet (PEJ) characteristics during the extreme May 2024 geomagnetic storms across dawn, dusk, daytime, and nighttime in both hemispheres. FACs and PEJ intensities were up to 9 times greater than usual, with equatorward FACs reaching −44° Magnetic Latitude. Maximum FACs and PEJ are larger at dawn than dusk in the Northern Hemisphere but larger at dusk than at dawn in the Southern Hemisphere. Dawn and duskside FACs correlate best with Dst or solar wind dynamic pressure (Pd) in both hemispheres. On the dayside (nightside), most FACs in both hemispheres are primarily correlated with Pd (merging electric field, Em or Pd). The PEJs correlate largely with Dst and partly with Em and Pd. Duskside (nighttime) currents are located at lower latitudes than dawnside (daytime), and northern currents are positioned more poleward than southern currents. The latitudes of peak FACs are most strongly correlated with Dst or Pd in both hemispheres. However, in the northern daytime sector, they are primarily influenced by Em. The latitudes of peak PEJ show the strongest correlation with Dst or Pd in both hemispheres, except on the northern dawnside, where they are primarily influenced by Em. The qualitative relationships between peak current density, corresponding latitude, solar wind parameters, and the Dst index are derived.