Influence of power line harmonic radiation on the VLF wave activity in the upper ionosphere: Is it capable to trigger new emissions?

We analyze the influence of Power Line Harmonic Radiation (PLHR) events on the overall VLF wave activity as observed by the low-altitude (about 700 km) DEMETER spacecraft. We take advantage of a unique set of 148 PLHR events identified in the Burst mode data, where a waveform of one electric and one magnetic field component is measured. It is shown that the occurrence rate of PLHR events over the industrialized areas is quite large (more than about 8%). However, among all the identified events, we have found only two cases of possibly PLHR-triggered emissions. There is no evidence that the total power spectral density of electromagnetic waves over industrialized regions and geomagnetically conjugate regions is larger than what would be expected without man-made influence. Finally, we have analyzed the presence of the weekend effect (i.e., a different behavior during the weekends as compared to the weekdays due to the lower power consumption), demonstrating that no such phenomenon seems to be present in the analyzed data set.