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Abstract 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.
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A 3‐D FDTD Methodology for Modeling the Propagation of VLF Whistler Mode PLHR Waves Through the Ionosphere
Abstract The finite‐difference time‐domain (FDTD) method was previously applied to high‐frequency electromagnetic wave propagation through 250 km of theFregion of the ionosphere. That modeling approach was limited to electromagnetic wave propagation above the critical frequency of the ionospheric plasma, and it did not include the lower ionosphere layers or the top of theF‐region. This paper extends the previous modeling methodology to frequencies below the critical frequency of the plasma and to altitudes encompassing the ionosphere. The following changes to the previous work were required to generate this model: (a) theD,Eand top of theFregions of the ionosphere were added; and (b) the perfectly matched layer absorbing boundary on the top side of the grid was replaced with a collisional plasma to prevent reflections. We apply this model to the study of extremely low frequency (ELF) and very low frequency (VLF) electric power line harmonic radiation (PLHR) through the ionosphere. The model is compared against analytical predictions and applied to PLHR propagation in polar, mid‐latitude and equatorial regions. Also, to further demonstrate the advantages of the grid‐based FDTD method, PLHR propagation through a polar cap patch with inhomogeneities is studied. The presented modeling methodology may be applied to additional scenarios in a straightforward manner and can serve as a useful tool for better tracking and studying electromagnetic wave propagation through the ionosphere at any latitude and in the presence of irregularities of any size and shape.
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- Award ID(s):
- 2434336
- PAR ID:
- 10630935
- Publisher / Repository:
- American Geophysical Union
- Date Published:
- Journal Name:
- Journal of Geophysical Research: Space Physics
- Volume:
- 130
- Issue:
- 2
- ISSN:
- 2169-9380
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript
- Journal Article:
- https://doi.org/10.1029/2024JA033273
