Drift of ionospheric scintillation irregularities at subtropical latitudes

Using simultaneous observations of VHF radio wave scintillations from two closely spaced satellites SIRIO at 650E, (transmitting on 136 MHz) and FLEETSAT at 730E (transmitting on 244 MHz) the characteristic properties of the ionospheric irregularities over a tropical station, Bombay (190N, 730E) have been deduced. It has been shown that usual E-W patch size observed at this latitude is of the order of 200-400 km, and these irregularity patches drift from West to East with a drift speed of about 170 m/s around 2100 h which decreases in the course of night, to about 60 m/s by 0500 h. Drift speeds at any time of the night are lower on magnetically disturbed than on quiet days