Diffraction from discrete and homogeneously structured ionospheric irregularities

Diffraction patterns produced by isolated irregularities have a maximum fading depth at radio frequencies near 0.6 ƒ T where ƒ T , the transition frequency, is a property of the electron density irregularity and marks the boundary between geometric and physical optics. A nearly homogeneous assembly of irregularities can produce scintillation which is speciously random. For such an assembly a peak in scintillation depth is also produced just below the mean f T . At radio frequencies below the scintillation is fast and frequency independent; above ƒ¯ T the amplitude pattern is directly related to the ionospheric structure.