Lunar-solar tides in electron density at fixed heights of the ionosphere

Lunar tidal variations in the electron density N at fixed heights of the ionosphere for different solar hours have been computed at the equatorial station Huancayo, and the mid-latitude station Puerto Rico. It is found that the tidal amplitudes increase rapidly with altitude between 180 and 250km. At Huancayo the phase i.e. time of maximum positive deviation of lunar semi-diurnal variations in N is 07-08 lunar hr for the lower regions (below 180 km); it changes sharply at heights around 200 km, above which it is 03-04 lunar hr. The amplitude of the tide at heights around 200 km is independent of solar hr. At Puerto Rico, the phase is continuously retarded with increasing height; it is about 01 lunar hr in E-region heights and changes to about 09-10 lunar hr at heights near h<SUB>max</SUB>. It is seen that lunar oscillations in the E- and F<SUB>1</SUB>-regions, at both the places, are in phase with corresponding magnetic field variations. Various observed results are explained as due to lunar variations in the magnetic field through the variations in the vertical electrodynamic drift velocities