[F1 layer] n (1933): the lower of the two layers into which the F region of the ionosphere splits in the daytime that occurs at varying heights from about 80 to 120 miles (130 to 200 kilometers) above the earth's surface
F1 LAYER
Meaning of F1 LAYER in English
Merriam-Webster English vocab. Английский словарь Merriam Webster. 2012