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Latitudinal and Hemispheric Responses of Solar Quiet Ionospheric Currents During Two Annular Solar Eclipses: Evidence From Low to Mid-Latitude Observations
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DOI：10.1029/2025JA034761.png)
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Abstract
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A sudden drop in solar radiation during an annular (or total) eclipse directly affects ionospheric electrodynamics, primarily through the reduction of solar extreme ultraviolet (EUV) and soft X-ray flux, which are responsible for generating the ionospheric plasma. The annular solar eclipses of 21 June 2020 and 14 October 2023 offer natural experiments under markedly different solar conditions. The 2020 eclipse occurred during a period of low solar activity (F10.7 = 70 s.f.u., Kp < 1), while the 2023 eclipse took place under higher solar activity levels (F10.7 = 147.4 s.f.u., Kp < 3), leading to stronger background solar-quiet (Sq) ionospheric current and more pronounced electrodynamic responses. Using global geomagnetic records from SuperMAG and coordinated networks, the Sq current and eastward current densities (Je) are estimated via spherical harmonic analysis techniques. The equatorial and low-latitude horizontal geomagnetic field variation (Delta H) decreased near maximum obscuration, with larger depletion in 2023 than in 2020, and smaller variations in the conjugate hemisphere. Concurrently, Je weakened by similar to 15% (2020) and similar to 25% (2023), while the equatorial electrojet (EEJ) changed 10%-30% with local-time phase shifts; the 2020 eclipse featured a transient EEJ enhancement, whereas 2023 showed suppression followed by delayed recovery. Maximum northern Sq current values decreased similar to 20% and southern minima similar to 13% in the 2020 eclipse, while the 2023 Sq current was similar to 65% stronger. The largest separation between northern and southern Sq current foci occurred during 2020 (similar to 2 h, similar to 30 degrees longitude; similar to 5 degrees latitude at 30 degrees N and 35 degrees S), whereas the 2023 eclipse exhibited smaller longitudinal (similar to 1 h, similar to 15 degrees longitude) but larger latitudinal (similar to 15 degrees, 30 degrees N and 45 degrees S) offsets.
Keywords:
ionosphere
geomagnetic field
solar-quiet ionospheric currents
equatorial electrojet
solar eclipse
electrodynamic coupling
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