SUMMARY OF EXTREMELY LOW-FREQUENCY (ELF) FIELD STRENGTH MEASUREMENTS MADE IN CONNECTICUT DURING 1975

Both 42‐ and 76‐Hz, horizontal, magnetic‐field‐strength measurements (amplitude and relative phase) were made in Connecticut during 1975. These measurements were taken to further investigate sunrise, daytime, sunset, nighttime, and seasonal extremely low frequency (ELF) propagation variations. The transmission source for these 1.6‐Mm range measurements was the US Navy ELF Wisconsin Test Facility. It was determined from these measurements that (1) ELF nighttime propagation is much more variable than daytime propagation, (2) the “Halloween effect” was observed for the sixth consecutive year, and (3) phase velocity changes during pure nighttime propagation conditions occasionally appear to be greater than changes associated with the sunrise‐sunset terminators crossing the transmitter or receiver locations. Copyright 1979 by the American Geophysical Union.