Geomagnetic activity and radio wave absorption in the equatorial region

Chukwuma, V. U. (2001) Geomagnetic activity and radio wave absorption in the equatorial region. Acta Geodaetica et Geophysica Hungarica, 36 (2). pp. 125-131. ISSN 1217-8977

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Abstract

Earlier investigations of the inuence of geomagnetic activity on radio wave absorption were based on storm selection criterion: SKp ³ 30. This criterion lumped together weak, moderate, and strong storms, and favouring weak and moderate storms made it impossible for the investigations to detect any change in equatorial radio wave absorption following geomagnetic storms. Presently, the effect of geomagnetic storms on equatorial radio wave absorption has been investigated using severe storms (Ap ? 54) and HF absorption data obtained at 4.87 MHz at 1000 hours LT at Lagos (3. 40^oE, 6. 55^oN). The absorption data were measured using radio waves reected from the F region, and the transmitter (Radio Cotonou) is located at Cotonou (2.43^oE, 6.35^oN). The present results obtained using the superposed epoch method show that HF absorption in the equatorial ionosphere increases after severe geomagnetic activity.

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