Tracking Electromagnetic Power Line Emissions and Harmonic Radiation from the Ground through Realistic, Inhomogeneous Three Dimensions (3-D) Ionospheric Conditions

Power grids are fundamental to modern civilization. However, power grids not only distribute electricity, but they also generate power line emissions (PLEs) at the fundamental frequency of 50/60 Hz as well as power line harmonic radiation (PLHR) at harmonic frequencies. These emissions propagate into and through the ionosphere where they can be detected by satellites. As power grids have continued to expand and increase in complexity over time, PLEs / PLHR have become widely recognized as a significant source of artificial electromagnetic pollution in the near-Earth environment. Physical measurements of PLEs and PLHR have been collected over many years, but conflicting conclusions have been made by different groups as the data has been analyzed. Further, there is a lack of agreement on the propagation mechanism of low-latitude (where most power grids are located) whistler mode waves (the propagation mode of PLEs / PLHR in the ionosphere). The research plans to undertake a systematic study to advance our understanding of how PLEs and PLHR couple to and propagate through the complex ionosphere to put these emissions on a firmer physical basis when they are measured either intentionally or unintentionally by satellites. Improving the quality of these studies is vital for developing more robust and advanced communication, remote sensing, ground-based backup navigation etc. All these systems are critical for our nation’s success. To help understand the behavior and characteristics of these power line emissions and higher frequency harmonics, the work aims at generating Maxwell’s equations models of how this noise propagates through the ionosphere, which is a magnetized plasma. Three specific objectives that are planned to be achieved by employing the robust, grid-based finite-difference time-domain (FDTD) method are: 1. Analyze the coupling of PLEs / PLHR from the atmosphere to the inhomogeneous ionosphere, especially for varying magnetic field directions and ducting conditions. 2. Determine the propagation mechanism for low-latitudes whistlers. 3. Characterize the impact of complex ionospheric inhomogeneities on PLEs / PLHR at varying altitudes and latitudes, such as equatorial plasma bubbles, ducts, and polar cap patches. The research will assist a wide variety of science missions to better anticipate and isolate PLEs and PLHR in their measured data. Numerous studies depend on electromagnetic measurements in the frequency range of PLEs and PLHR, including studies of lightning, sprites, the Van Allen radiation belts, and the effect of solar and cosmic activity on the ionosphere. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.