Influence of Geomagnetically Induced Currents on Power Line Harmonic Radiation Observed at the Kannuslehto Ground‐Based Station

Abstract

This study investigates the properties of power line harmonic radiation (PLHR), a type of electromagnetic emission generated by electric power networks. In particular, we analyze how the PLHR intensity varies in relation to geomagnetically induced currents (GICs), quasi‐DC currents driven by rapid changes in the geomagnetic field during space weather events. High‐resolution very low frequency wave measurements from the ground‐based Kannuslehto station in northern Finland are used to determine the PLHR power spectra. Local horizontal magnetic field variations are derived from the nearby SOD magnetometer data and are used as a proxy for the GIC magnitude. We show that PLHR is continuously present and almost independent of local time. During quiet conditions, the PLHR intensity at odd harmonics is significantly larger than the PLHR intensity at even harmonics. However, at periods of strong local magnetic field fluctuations, the PLHR intensity enhancement at even harmonics and triplen harmonics increases drastically, by several orders of magnitude. This demonstrates a clear control role for GICs in the generation of PLHR.