11:15 〜 11:30
[PEM14-09] Geomagnetic Responses to Solar Eclipses: Observations from the 2023 and 2024 Solar Eclipses in the Continental United States
キーワード：Solar eclipses, Geomagnetic variations, Ground-based magnetometers, Sq current, Ionosphere, Field line resonance
Previous studies have shown that solar eclipses can cause small but observable changes in the geomagnetic field at ground level near the eclipse path. It has been suggested that these changes result from the obstruction of electric currents in the shadowed ionosphere and possibly the excitation of an eclipse-induced interhemispheric field-aligned current. Additionally, a solar eclipse may impact the resonance of magnetospheric field lines connected to the eclipsed ionosphere due to asymmetry in ionospheric conductivities between the two hemispheres. However, these hypotheses require further observational confirmation.
In this study, we present network observations from the MagStar, SMART, TAMU, and USGS magnetometer arrays in the United States during the 2023 annular and 2024 total solar eclipses. We found that magnetometer stations within the Moon’s shadow detected changes of up to approximately 10 nT (20 nT) in the north-south component during the 2023 (2024) eclipse. In both events, the eclipse-induced perturbations suggest the presence of a westward equivalent current in the ionosphere, consistent with the obstruction of the low-latitude eastward Sq current due to reduced ionospheric conductivity. However, our observations do not show a clear eclipse signature in the east-west component, as predicted by theory.
During the 2024 total solar eclipse, the SMART team conducted the first known live geomagnetic watch of a solar eclipse, with more magnetometer stations positioned near the path of totality. The combined data show that eclipse-induced magnetic perturbations were stronger at lower latitudes but were not discernible in the northeastern United States. Additionally, the UCLA magnetometer at Palmer Station, Antarctica -- magnetically conjugate to New Hampshire/Maine -- did not observe any magnetic field changes associated with the northern hemisphere eclipse. These results suggest that a pre-existing ionospheric current is necessary for eclipse-induced magnetic field perturbations.
Furthermore, in both solar eclipse events, network magnetometer data revealed that field line resonance signatures disappeared during the eclipse, indicating that reduced ionospheric conductivity at one end of a magnetospheric field line can rapidly disrupt resonance.
In this study, we present network observations from the MagStar, SMART, TAMU, and USGS magnetometer arrays in the United States during the 2023 annular and 2024 total solar eclipses. We found that magnetometer stations within the Moon’s shadow detected changes of up to approximately 10 nT (20 nT) in the north-south component during the 2023 (2024) eclipse. In both events, the eclipse-induced perturbations suggest the presence of a westward equivalent current in the ionosphere, consistent with the obstruction of the low-latitude eastward Sq current due to reduced ionospheric conductivity. However, our observations do not show a clear eclipse signature in the east-west component, as predicted by theory.
During the 2024 total solar eclipse, the SMART team conducted the first known live geomagnetic watch of a solar eclipse, with more magnetometer stations positioned near the path of totality. The combined data show that eclipse-induced magnetic perturbations were stronger at lower latitudes but were not discernible in the northeastern United States. Additionally, the UCLA magnetometer at Palmer Station, Antarctica -- magnetically conjugate to New Hampshire/Maine -- did not observe any magnetic field changes associated with the northern hemisphere eclipse. These results suggest that a pre-existing ionospheric current is necessary for eclipse-induced magnetic field perturbations.
Furthermore, in both solar eclipse events, network magnetometer data revealed that field line resonance signatures disappeared during the eclipse, indicating that reduced ionospheric conductivity at one end of a magnetospheric field line can rapidly disrupt resonance.