Lower Ionospheric Disturbances Derived from Measurements of VLF Transmitter Signals

D-region specifically corresponds to the altitude range of 60 to 90 km, a partially-ionized region that resides between the neutral atmosphere (<60 km) and the more ionized atmosphere (>90 km). It is, in nature, influenced not only by solar radiation, cosmic rays and energetic particle precipitation from the upper, but atmospheric waves from the lower atmosphere. Measurements of Very Low Frequency (VLF) signals from navy transmitters carry direct information about the D-region ionosphere and have been widely utilized to detect the electron density at D-region altitudes. Atmospheric waves have been extensively studied, but if and how they are correlated with the D-region ionosphere and VLF measurements still remains poorly investigated. In this study, we combine VLF measurements with WACCM-X modeling to investigate lower ionospheric disturbances related with atmospheric waves. We conduct a comprehensive analysis using 7-years measurements (2016-2022) of VLF signals from the JJI, NWC, and VTX transmitters as being recorded in Suizhou, China. The results show that the prominent periodicities ranging from 2 to 730 days, with clear diurnal variation and latitudinal/longitudinal dependence. Additionally, the gravity wave-like perturbations observed from the VLF signals measured by the Great Wall Station in Antarctica are supposed to be modulated by semi-diurnal and diurnal tides. Our work reveals the potential link between VLF signals and atmospheric waves, offering new insights into the propagation/evolution of atmospheric waves, which contributes to the further study of multi-layer coupling in near space environments.