Spatiotemporal Characteristics of the Nighttime High-Latitude Ionospheric Electric Field Based on CSES Observations

The ionospheric electric field is a crucial parameter in magnetosphere–ionosphere coupling, and its spatiotemporal distribution is fundamental to understanding space electrodynamics and space weather evolution. This study utilizes one year of revisit-orbit observations from the Electric Field Detector (EFD) aboard the China Seismo-Electromagnetic Satellite (CSES) to systematically analyze the spatiotemporal characteristics of the nighttime high-latitude ionospheric electric field in the Earth-Centered Earth-Fixed (ECEF) coordinate system. First, waveform data for the three electric field components were preprocessed, and their statistical distributions over a full year were analyzed across latitudes from 65°S to 65°N. Subsequently, temporal variations of the Y-component (Ey) were examined at selected fixed latitudes to characterize its annual evolution. In parallel, power spectral density (PSD) data from the EFD’s VLF band were used to investigate the latitudinal and temporal patterns of electric field disturbance energy in the 11.5–12 kHz range. The results reveal that, under fixed revisit-orbit conditions, the three electric field components exhibit a stable large-scale spatial structure as a function of latitude. Among them, Ey is the most sensitive indicator of electric field variations, displaying pronounced stage-like annual variations at fixed latitudes, with the amplitude increasing toward higher latitudes. In the VLF band, the PSD generally exhibits a latitudinal pattern characterized by stable values at middle latitudes and enhanced intensities at high latitudes, where significant electromagnetic disturbances are more likely to occur. These findings demonstrate that the nighttime high-latitude ionospheric electric field and its associated electromagnetic disturbance energy exhibit pronounced spatiotemporal variability on an annual scale. This study provides new observational evidence from satellite measurements for understanding high-latitude ionospheric electrodynamics and magnetosphere–ionosphere coupling mechanisms.