Localized ELF nocturnal propagation anomalies


  • Peter R. Bannister


On numerous occasions during the last decade, extremely low frequency nighttime field strength measured at various sites in the northeastern United States has displayed rapid decreases of from 4 to 8 dB in several hours. In this article we present further examples of localized ELF nighttime field strength variations and show that these variations are not restricted to measurement locations in the northeastern United States. Particular attention will be focused on simultaneous Connecticut and North Atlantic area measurements where nighttime propagation anomalies occurred 2–4 hours apart. A candidate for the cause of these anomalies is a moving nocturnal sporadic E layer.