Some studies on the ionospheric absorption at Waltair

The results of absorption measurements made on frequencies 2·0 Mc/s, 2·5 Mc/s and 3·0 Mc/s at Waltair (Geog. Lat. 17°43'N, Long. 83°18'E, Geomag. Lat. 7·4°N) during the period January 1963 to February 1965 are presented. The main aspects studied are (i) diurnal variation of absorption, (ii) the relative contributions of D- and E-region absorptions, (iii) sunspot variation of absorption and (iv) effect of magnetic activity on absorption. The value of cos [chi] index n for the diurnal variation of absorption on 2·0 Mc/s is found be 0·8. The relative contributions of D- and E-regions to 2·0 Mc/s absorption are estimated and it is found that the D-region contribution consists of two parts, one depending on the solar zenith angle and the other independent of it. The results of correlation between the absorption and magnetic activity are presented and it is found that the effect of magnetic activity is more at higher levels of the absorbing stratum when compared to that at lower levels.