Diurnal Variation of Ionospheric Absorption over Calcutta

Abstract

A detailed investigation on the diurnal variation of ionospheric absorption over Calcutta at various frequencies (over Calcutta) shows that the absorption fits better with the relation Loccosn x rather than with L=A+Bcos x, with the n values lying between 0.9 to 1.9 for different frequencies and seasons. The frequency dependence of the exponent n depends critically on the relative amount of the deviative and non-deviative losses.The diurnal variation of absorption also shows some asymmetry between the forenoon and afternoon values, the index n for the forenoon values being always greater than the afternoon values. The possibility of geomagnetic control over at least a part of the absorbing region has been invoked.

Global features of lower ionospheric radio wave absorption in relation to middle atmospheric temperature variation and wind circulation

“…Theoretically the ionospheric absorption is expected to follow some function of the solar obliquity, e.g., cos X [Jaeger, 1947] and the dependence of absorption on solar zenith angle X is conventionally represented as proportional to some power of cos X-Though a relation of this form is representative of the situation over a day [ Khastgir et al, 1973 ], the large-scale composition changes over a year make the solar dependence throughout the season somewhat complicated. Nevertheless, it has been the usual practice of many pioneering Figure 1 both for the low and high solar activity conditions.…”