Seasonal variation of the lunar tidal effects in the F₂ layer of the ionosphere over Indian stations

Abstract

The lunar semi-diurnal oscillations in the midday values of the critical frequency (ƒ₀F₂) and the height of maximum electron density (h_pF₂) of the F₂ layer are computed for all Indian ionospheric stations separately for each season of the year. The amplitude of oscillation in ƒ₀F₂ is found to be larger in winter than in summer at each of the stations. There is a reversal in the phase of the oscillation in ƒ₀F₂ between the equatorial and tropical latitudes and this is most evident in the winter months and is almost absent in summer. The annual average oscillation in ƒ₀F₂ is in agreement with that found in a previous paper (Rastogi, 1961). The phase has a large seasonal variation of about 180° at an equatorial or a tropical latitude station. The phase and amplitude of the lunar tide in h_pF₂ do not vary significantly with latitude or with season.