Comparison of ULF electric field recorded by ground-based stations in China and a low-altitude satellite
Abstract
The correlation and synchronization between ground-based and space-based electric field in calm period, is the basis for a comprehensive study of earthquake monitoring. However, it is difficult to study their relevance because of large dissimilarities on data records. The DC-ULF electric field recorded by the DEMETER satellite and the geo-electric field observed in ground-based stations in China were comprehensively analyzed in this paper. The results show that the ionospheric electric field after removing the additional electric field caused by the satellite motion in the magnetic field has a stable annual variation trend; both the annual variation trend and the amplitude of ionospheric electric field above different locations in China are similar. The synchronous, corresponding and similar significant annual variation trends of both ionospheric electric field and geo-electric field in the same direction and with same frequency were found above some locations. The trend displays higher value in summer and lower value in winter. The Sq (Solar quiet) current system is the main source for these phenomena. It is noticed that the shapes and amplitude of geo-electric field for different stations are different, largely due to their individual underground layer conductivity, water level and so on. It is of great significance to explore the correlation and consistency between ground-based and space-based data in order to recognize the anomalies related to the seismic activity and to understand the LAI (Lithosphere-Atmosphere-Ionosphere) coupling mechanism.
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