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ABSTRACT
The results of ionospheric absorption measurements at Ahmedabad (23°01'N, 72°36'E) on 2·6 Mc/s. by vertical pulse reflection method from May 1965 to April 1966 are presented in this paper.
The following are the main conclusions:
| (1) | The absorption rises after sunrise and reaches maximum at noon. From sunset to sunrise the absorption is very small, almost 10 per cent of the noon value. | ||||
| (2) | The mean monthly mid-day values of absorption show seasonal variation: minimum in winter and maximum in summer. The summer maximum is broader than winter minimum. | ||||
| (3) | The absorption is found to vary with cos χ according to the relation
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| (4) | The overall absorption in 1965–66 was reduced to 34 per cent of the absorption in 1957–58. | ||||
| (5) | The absorption values extrapolated for cos χ = l show a liner relation with sunspot number of the type L = L0(1 + bR), where 0 = 35 db., b = 0·006 | ||||
| (6) | During the solar eclipse, the absorption was significantly lower than that in the normal days. | ||||