Diurnal and seasonal variation of fading rates of E- and F- region echoes during IGY and IQSY at the equatorial station of Ibadan

Abstract

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Fading rates of E- and F-region echoes observed at Ibadan (7.4°N, 3.9°E, 6°S dip) during the International Geophysical Year (IGY) 1958 and the International Quiet Year of the Sun (IQSY) 1964 are investigated for diurnal and seasonal variations. The fading rates of E- and F-region echoes are found to be of the same order of magnitude during the IQSY. However, the same is not true during IGY indicating that fading of F-region echoes is dependent on solar activity while that of E-region echoes is not as fading rate of E-region echoes are about the same during both epochs. The fading rate is found to be maximum at noon and minimum at sunrise and sunset for E-region echoes during both epochs and for F-region echoes during IQSY. During IGY, fading rate is maximum at noon; and minimum at sunrise and 2000 hrs LT (i.e. post sunset) at both epochs and for the two regions about same times of reversal of F-region East-West (EW) and E×B vertical drift during solar maximum. The maximum at noon appears to be due to: (i) continuous daytime rise in hmF2 which enhances irregularities and (ii) spread F irregularities generated by sudden increase in E×B plasma uplift not seen by the close-spaced antenna technique used in the present study. F-region fading rate is maximum during December solstice while E-region fading rates show no seasonal variation.</smarttagtype></smarttagtype>