IEVref: 705-07-73 ID: 705-07-73 Language: en Status: Standard Term: critical frequency, Synonym1: Synonym2: Synonym3: Symbol: Definition: highest frequency at which a radio wave undergoes reflection in an ionospheric layer on which it is incident vertically Note 1 to entry: There is usually one critical frequency for each magneto-ionic component Note 2 to entry: The critical frequency for the ordinary wave is the plasma frequency corresponding to the maximum electron density of the layer. Note 3 to entry: The critical frequencies for the ordinary wave and the extraordinary wave are respectively represented by the symbols fo and fx, followed by the designation of the layer, for example: foF2. Publication date: 2014-11 Source: Replaces: 705-07-73:1995-09 Internal notes: CO remarks: TC/SC remarks: VT remarks: Domain1: Radio wave propagation Domain2: Influence of the ionosphere on radio wave propagation Domain3: Domain4: Domain5: