Abstract
Abstract. It has been suggested that the space environment is being polluted by power line harmonic radiation (PLHR), generated from harmonics of the electrical power transmission frequency (50 or 60 Hz) and radiated into the ionosphere and magnetosphere by long power lines. While some in-situ satellite measurements of PLHR have been reported, it has proved difficult to confirm the source and overall significance. The electricity network of the city of Dunedin, New Zealand, is tiny compared to the many large industrial zones found outside New Zealand. However, the 1050Hz ripple control signal injected into the local electrical grid at regular intervals as a load-control mechanism provides an opportunity for identifying PLHR strengths radiated from a spatially well defined electrical network. In-situ observations by satellites should allow a greater understanding of PLHR and its significance as man-made pollution to near-Earth space. Calculations have been undertaken to estimate the strength of the radiation fields expected from the ripple control signal which is injected into the Dunedin city electrical network. We find that ground-based measurements will not be sensitive enough for detection of the ripple control radiation fields, even during the quietest winter night. While significant power penetrates the lower ionosphere, this is well below the reported threshold required for nonlinear triggering in the Van Allen radiation belts. Some radiated fields at satellite altitudes should be detectable, allowing in-situ measurements. At the altitude of the DEMETER mission, the radiated electric fields will not be detectable under any ionospheric conditions. However, we find that the radiated magnetic fields may be detectable by the DEMETER satellite at certain times, although this will be very difficult. Nonetheless, there is the possibility for future experimental campaigns. Keywords. Magnetospheric physics (Magnetosphereionosphere interactions; Plasma waves and instabilities) – Ionosphere (Active experiments)
Highlights
There are experimental reports indicating that radio waves from long electrical transmission lines may leak into nearEarth space and modify the space environment (e.g. Bullough, 1995; Parrot and Zaslavski, 1996)
The identification of 1050 Hz signals in satellite observations above Dunedin city during ripple control injection times would allow the clear identification of power line harmonic radiation (PLHR) from a known source
The Dunedin city electrical network is tiny compared to the many large industrial zones found outside New Zealand
Summary
There are experimental reports indicating that radio waves from long electrical transmission lines may leak into nearEarth space and modify the space environment (e.g. Bullough, 1995; Parrot and Zaslavski, 1996). An experimental VLF transmitter located in Antarctica has previously been used to simulate the PLHR in near-Earth space These experiments indicated a radiated power threshold of ∼1 W (Helliwell et al, 1980), where higher powers lead to the observation of nonlinear triggered emissions (Park and Chang, 1978) indicating strong interactions between waves and trapped particles. Ohzora satellite observations appeared to include Japanese PLHR at 50 and 60 Hz (Tomizawa and Yoshino, 1985) This identification was possible due to the mixed nature of the Japanese electrical grid, where 50 Hz is used in the northern “half” of the country, and 60 Hz in the south. In this paper we examine the calculated radiated fields expected from the ripple control signal in the Dunedin city electrical network at ground level, the base of the ionosphere, satellite level and in the equatorial plane in the magnetosphere. Our primary goal is to examine the expected signal strength at satellite altitudes, and contrast these with the detection thresholds of in-situ observational missions
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