Regularities in the Behaviour of Some Anomalies in F₂-Region

110-113The ratio of the electron density existing at any time to the calculated electron density at the level of maximum electron production for solar zenith distance =0, has been computed for F2-layer heights from observed data at Thumba and Ahmedabad. The residue obtained after subtracting the theoretical Chapman value from the actual value, when subjected to harmonic analysis yields prominent periodicities. Seasonal effect in the periodicities is found to depend on latitude and is simpler near the equator than at higher latitudes