An Ion and Electron 3D FDTD Model Investigation Into Ionospheric ELF EM Wave Propagation From Power Lines

Power line harmonic radiation (PLHR) is a continuous source of electromagnetic energy in the near‐Earth environment. However, it is currently unknown why certain PLHR frequencies are more likely to reach satellites under specific ionospheric conditions. A significant factor likely influencing this behavior is the presence of ions, which can attenuate whistler modes and introduce additional wave modes that can impact PLHR propagation characteristics. Building on previous work that studied very low frequency PLHR propagation through an electron‐only ionosphere, this study employs a three‐dimensional finite‐difference time‐domain model comprised of both electrons and ions to investigate powerline emission and PLHR behavior at 60 Hz and higher harmonics. Two key advancements are introduced relative to the earlier work: (a) two ion profiles are incorporated into the model up to 1,000 km, and their impact is examined; and (b) an enhanced collisional plasma formulation designed for magnetized plasmas containing both electrons and ions is developed for the top of the grid to avoid reflections. The model is validated against analytical solutions and applied to PLHR propagation across polar, mid‐latitude, and equatorial regions. Results demonstrate that the ion composition plays a significant role in wave transmission, particularly when the PLHR source frequency approaches or falls below the ion gyrofrequency cutoff, resulting in notable changes in the electric field amplitudes at certain altitudes. These findings offer insight into the frequency‐selective nature of PLHR detection observed in satellite data. The modeling framework is adaptable, providing a valuable tool for studying electromagnetic wave behavior in different ionospheric environments.