Stationary large-scale irregularities of the ionosphere

Ionospheric absorption measurements (Al method) made in the course of eight voyages by Soviet and other research vessels indicate that the global distribution of absorption shows a distinctive regional structure. Areas of abnormally high absorption in the neighbourhood of the equator have been located in the Pacific near the west coast of South America and in the Indian Ocean. The west Mediterranean area also shows abnormally high absorption. In some cases these areas of high absorption appear to coincide with areas of low nocturnal F-region electron density.