Key points are not available for this paper at this time.
Records are reproduced showing diffuse echoes from the F ‐region of the ionosphere received continuously at night in equatorial regions over a wide range of wave‐frequency. Tney are interpreted as due to Rayleigh scattering by spatial irregularities in the distribution of electron‐density at or above a definite level in the F ‐region. Because of the highly dispersive nature of the ionosphere, there is no marked dependence of Rayleigh scattering upon wave‐frequency such as there is for a non‐dispersive medium. According to this interpretation, variation of the maximum wave‐frequency to which diffuse echoes can be followed has nothing to do with variation of the maximum electron‐density of an ionospheric region, but merely indicates variation in the size of irregularities in electron‐density. Scattering of this type may have some bearing upon the phenomenon of persistence of E ‐region echoes to wave‐frequencies greater than the critical penetration‐frequency of the E ‐region.
Booker et al. (Thu,) studied this question.