Qinzhong Ma

Geomagnetically induced geoelectric fields can exhibit substantial spatial variability because regional subsurface electrical structures affect surface electromagnetic responses. This study characterized the induced geoelectric field across mainland China during the extreme geomagnetic storm of 10 May 2024, using observations from the China Geoelectric Network. We evaluated changes in field intensity, ratios between collinear short- and long-dipole measurements, and regional variations in polarization direction, with particular emphasis on the onset of the storm. The geoelectric response showed pronounced spatial heterogeneity, with substantial differences among stations during storm onset. At most stations, measurements from collinear short and long dipoles maintained consistent ratios, indicating stable local scaling between the two electrode configurations. In contrast, polarization directions inferred from the long-dipole measurements showed no uniform relationship with local land–sea orientations. High-density electrical exploration data further supported this interpretation. These findings indicate that local subsurface electrical structures play an important role in controlling geoelectric field measurements and their responses to geomagnetic disturbances. This study provides a quantitative assessment of storm-time geoelectric field variations across mainland China and establishes a basis for investigating regional electromagnetic phenomena associated with induced geoelectric fields.

In this paper, we analyze the characteristics of the induced geoelectric field in mainland China during the extreme magnetic storm from May 10–12 2024, based on the data from China Geoelectric Network. Our analysis focuses on the magnitude of the induced geoelectric field changes, the ratio between isotropic short and long dipoles, and the variation in polarization direction across different regions during the sudden onset of the magnetic storm. Our study reveals that horizontal changes in the induced geoelectric field intensity are not confined to specific regions during the sudden onset magnetic storms. When analyzing the same-direction ratio, at most stations it showed a consistent ratio between short and long dipoles. The polarization orientation derived from long-dipole ratios suggests that there is no consistent alignment of land and sea directions on the ground surface. These results indicate that the variations in geoelectric field measurements are influenced by the underlying electrical structure at each station. These findings are further interpreted by using high-density electric exploration data. This paper provides a quantitative characterization of changes in the induced geoelectric field intensity across mainland China during the geomagnetic storms, offering a foundation for further analysis of regional geoelectric field electromagnetic phenomena.