Irregularities in the ionosphere

Electron clouds, both in the E and F regions of the ionosphere, have been detected at vertical incidence by means of a high-precision ionosphere sounding equipment. The clouds give rise to scattered echoes, which are delineated on an expanded sweep as individual pips, resolved out from the normal echoes. An estimate of the received power by back-scattering, made on the basis of the theory of tropospheric radio scattering by Booker and Gordon, shows that it is far in excess of the receiver noise power. Some of the records indicate that sometimes at night the normal layer structure of the ionosphere ceases to hold; the ionospheric regions then contain only electron clouds at different heights. The scattered echoes generally appear for a very short duration. The short persistence (1 to 2 minutes) of these echoes has been explained by considering the drift of the clouds by the upper air winds.