The Northern Hemisphere AARDDVARK network. The green circles are the VLF transmitters, the red diamonds are the AARDDVARK receivers. The green lines show the great circle paths between the transmitters and the receivers. The dashed black oval shows the magnetic latitude of the footprint of the expected quiet-time average plasmapause position in terms of the McIlwain L-shell parameter (in this case L = 4.5). The four new stations installed in PLASMON are Forks (Seattle, USA), Ottawa and St. John’s (both in Canada), and Eskdalemuir (Scotland).