Ionospheric Total Electron Content over the Magnetic Equator (Kodaikanal) during Half a Solar Cycle

16-21The total electron content (TEC) in the ionosphere using Faraday rotations of Sss satellites for the equatorial latitude station, Kodaikanal, is described. The daily variation of TEC shows a minimum around 0400-0500 hrs LT and a maximum around 1400-1600 hrs LT. There is no indication of noon bite-out in TEC except during summer of high sunspot years. The equivalent slab thickness is about 200 km during nighttime hours and about 400 km around midday hours. The ratio of TECs in top and bottom layers of the ionosphere (Na/Nb) is about 2'0 during daytime hours. In the nighttime of high sunspot years this ratio exceeds 4.0. Both the slab thickness and TEC show equinoctial maxima. The TEC shows linear positive relationship with solar flux but the slab thickness is rather constant with changes in solar flux