MULTISTATION VHF SCINTILLATION STUDIES AT LOW LATITUDES

Amplitude scintillations data at 244 MHz (FLEETSAT, 73 degrees E) reco rded from a network of three stations at Waltair (17.7 degrees N, 83.3 degrees E), Nuzvid (16.8 degrees N, 80.8 degrees E) and Payyanur (12 degrees N, 75.8 degrees E) from August 1991 to April 1993 are used to study the characteristics of ionospheric irregularities at low and nea r-equatorial latitudes in the Indian sector. The occurrence and patch durations are found to be higher at the near-equatorial station Payyan ur, when compared to the occurrence at the other two low latitude stat ions. Equinoctial maxima are seen at all three stations followed by se condary maxima in winter. However during summer, significant scintilla tions were present at Payyanur, while the occurrence is much reduced a t the other two low latitude stations. Scintillations are also inhibit ed during magnetically disturbed days. The scintillation patches recor ded at the two nearby low latitude stations (Waltair and Nuzvid) show similarities during post-sunset hours, while their characteristics are found to differ after midnight. From a comparison of similar patches simultaneously recorded at the above two nearby stations, the velocity components of the drift of ionospheric irregularities are found to sh ow predominent eastward movements with velocities varying between 80 a nd 280 m s(-1). The occurrence of daytime scintillations is found to b e higher in summer months. Copyright (C) 1996 Elsevier Science Ltd