|Definition:|| the magneto-ionic component which, at vertical incidence, is reflected at the height at which the electron density and the Earth's magnetic field are such that:|
fp2 = f 2 + f f B
where fp is the plasma frequency, f is the wave frequency, and f B is the electron gyro frequency
NOTE 1 – This component may appear when the direction of propagation of the wave is close to the direction of the Earth's magnetic field, or when the wave frequency is less than the electron gyro-frequency, and also in top-side ionospheric sounding.
NOTE 2 – The polarization of this component is either that of the ordinary wave, or that of the extraordinary wave, depending on the value of its frequency relative to the values of the plasma frequency and electron gyro-frequency on the wave path before reflection.