“…Plasma density irregularities in the equatorial ionosphere have long been studied since the starting of the research of spread F phenomena using many kinds of techniques such as ionosondes (RASTOGI, 1980a(RASTOGI, , 1980b and radar backscatter techniques (FARLEY et al, 1970;WOODMAN and LAHOZ, 1976;TSUNODA, 1980aTSUNODA, , 1980bTSUNODA, , 1981TSUNODA and WHITE, 1981;TSUNODA et al, 1979 as well as using spacecrafts as rockets (SZUSZCZEWICZ et al, 1980(SZUSZCZEWICZ et al, , 1981RING et al, 1981;NARCISI and SZUSZCZEWICZ, 1981;KELLEY et al, 1982) and satellites (CLARK and RAITT, 1976;MCCLURE et al, 1977;MULDREW, 1980;BENSON, 1981). One of the remarkable outcome of these observations is the discovery of plasma bubbles in the region of the equatorial F region ionosphere.…”