Lower Ionospheric Response to IMP Polarity Reversals

273-276Noon measurements of radio wave absorption in the ionosphere available at Colombo, Waltair and Kokubunji over long periods of time are employed in the study of the effect of IMF polarity reversals on the lower ionosphere at tropical and middle latitudes. Nearly 60% of the reversals are found to give rise to modest enhancements in absorption. This percentage is a little higher for positive to negative reversals as compared to that for negative to positive events. Mesospheric heating due to increased geomagnetic activity following a reversal is suggested as the possible mechanism behind absorption enhancements