(n)the highest region of the ionosphere (from 90 to 600 miles up) which contains the highest concentration of free electrons and is most useful for long-range radio transmission, Syn.F region, F layer
[阿普尔顿 / 阿普爾頓, Ā pǔ ěr dùn, ㄚ ㄆㄨˇ ㄦˇ ㄉㄨㄣˋ]Appleton (name); Sir Edward Appleton (1892-1965), British physicist, Nobel laureate who discovered the ionosphere#319182[Add to Longdo]