On the nonlinear triggering of VLF emissions by power line harmonic radiation

VLF ground data from Porojarvi in N. Finland has been presented. Spectrograms reveal frequent occurrence of power line harmonic radiation (PLHR), originating from the Finnish power system and from heavy industrial plant. The radiation is seen to penetrate the magnetosphere since numerous occurrences of PLHR triggered emissions are seen. Risers predominate but fallers and hooks are also observed. A well-established 1D Vlasov simulation code has been used to simulate these emissions, using plausible magnetospheric data for a range of L values from L = 4 to L = 5.5. The code is able to reproduce risers fallers and hooks in close agreement with observations. The results shed considerable insight into the generation structure of both risers and fallers.