Analysis and interpretation of spaced receiver scintillation data recorded at an equatorial station

Ultrahigh frequency satellite signals from the Pacific FleetSat (53° elevation angle) and L band signals from the Pacific Marisat (50° elevation angle) were recorded in Guam, an equatorial station, from April 1982 through May 1, 1983. Three receivers aligned in the magnetic east‐west direction were used, with the most widely separated receivers (457.2 m separation) recording the UHF signal amplitudes and the middle receiver recording the L Band signal amplitudes. These data are analyzed for the drift characteristics of ionospheric irregularities. The digitized spaced receiver data are processed to yield the scintillation index, the cross‐correlation function and the self‐power spectrum. By assuming a locally frozen flow, several methods have been devised to compute the drift velocity, V₀, and the characteristic random velocity, V_C. These methods seem to show internal agreement. They also show that the velocity fluctuations decrease markedly during the first few hours after local sunset. The spectral index of the self‐power spectrum roll‐off was also determined during times of both weak and strong scintillation. For the weak scintillation cases, the slopes were observed to gradually steepen as the night progressed into the postmidnight period. This steepening suggests the decaying of smaller‐sized irregularities. There were a few exceptions to this observed decay. For the strong scintillation cases, the shape and slope of the self‐power spectrum were observed to be influenced by the drift velocity and scattering strength of the irregularities.