Diurnal variation of ionospheric absorption over Calcutta

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 L∝cosn χ rather than with L=A+Bcos χ, 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.