the highest of the radio-reflective ionospheric layers, beginning at an altitude of about 80 miles (130 km) and consisting of two parts, the lower part (F layer) being detectable in the daytime only, the higher (F layer or Appleton layer) being constant and constituting the ionospheric layer most favorable for long-range radio communication.
Origin of F layer
First recorded in 1925–30
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
See F region.
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