Sporadic echoes from the E region over Ahmedabad (28° 02′ N, 72° 38′ E)

Abstract

In this paper, a study is made of the sporadic E echoes observed in the ionospheric h′-ƒ records of Ahmedabad ( Φ = 13.6° N). From the analysis of the data for 1953–1954, a sunspot minimum period, it was found that three types of sporadic, namely 1. (i) Esc at 95–100 km, 2. (ii) Esn at 105–125 km, and 3. (iii) Ess at 115–125 km, occur in the E region. The overall behaviour of Es has been shown as being due to the combination of the characteristics of these three types. The sporadic ionization of type Esc has a maximum frequency of occurrence in the late evening hours, and has a thin structure. It is apparently evolved out of a downward drift of the residual ionization of the normal E layer. No correlation could be established with meteor activity. Esn shows a minimum in the afternoon and maximum in late-night hours before dawn. Ess is developed by the vertical downward movement of the E2 layer.