A new interpretation of the VLF impedance measurements of island slot antennas

It was first suggested by Morgan in 1960 that an island might serve as a naturally resonant VLF slot antenna. However, theoretical studies by Galejs and Staras suggest that the principal current path would not be, as hoped, the ocean looping around the ends of the island. Rather the current would be confined to a region of the order of 1 skin depth radius centered on the conductor coupling the VLF power to the island. This is in conflict with the recent observations of Morgan, who claims to have observed resonances in the impedance of Deception Island. It is suggested here that these resonances are in fact resonances of the transmission lines used to connect power to the island. A similar explanation is also offered for the peninsula resonances observed by Gould. With this interpretation the experimental data on island antennas is fully in agreement with the current theoretical predictions of Galejs and Staras.