Abstract Previous research has established that in geospace, the total electron content (TEC) in the ionosphere can be modulated efficiently by ultralow frequency (ULF) waves in high‐latitude regions. However, the correlations between TEC variations and ULF waves in middle‐latitude and low‐latitude regions remain inadequately explored. In this study, using ground‐based magnetometer data from the Chinese Meridian Project, we identified ULF wave events within Pc4 frequency bands in the midlatitude region. During the period from 1 July to 30 December 2023, we identified 642 distinct ULF wave events in the Pc4 band, thereby creating a comprehensive ULF wave database. Statistical analysis indicated that Pc4‐band ULF wave events predominantly occurred on the night side in midlatitude regions. Notably, on 24 August 2023, simultaneous observations of geomagnetic disturbances and TEC disturbances at a similar frequency were recorded, suggesting a potential correlation between Pc4 ULF waves and TEC variations at midlatitudes. Through quantitative analysis, we infer that ionospheric TEC variations were triggered by Pc4 ULF waves during this event and the mechanism underlying this may be the horizonal plasma density gradient. This result provides direct observational evidence of the modulation of the TEC by Pc4 ULF waves in the midlatitude region. Furthermore, multiple additional TEC modulation events associated with ULF waves were identified, substantially reducing the likelihood of coincidental occurrence and reinforcing the validity of our findings. These findings broaden our understanding of the coupling between the solar wind‐magnetosphere‐ionosphere in midlatitude regions, and may be significant for evaluating the effect of space weather of this coupling process.
Cheng et al. (Wed,) studied this question.