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Related to F2 layer: F1 layer
The upper layer of the ionosphere, it lies between 110 to 210 miles (180–350 km). The F2 layer is more persistent than the F1 layer. Its height varies in summers and winters as well as during the days and nights. It affects daytime propagation and reflects waves from about 3 to above 30 MHz. Also called the Appleton Layer. See F layer.