A Review on Equatorial Ionospheric Irregularities

This paper provides an overview of the current knowledge of Equatorial F2-rgion Ionospheric Irregularities (EFI) with emphasis on local time, seasonal and geomagnetic influences. The existence of ionospheric irregularities in the plasma density structure may cause severe fluctuations in the amplitude and phase of radio signals propagating through such structure leading to degradation of the signal or complete reception failure. Its development, which has been linked to plasma instabilities, is usually observed around the post-sunset period and has been found to be most severe around the equatorial regions. Understanding the complex nature of the morphology of EFI across different equatorial regions of the world is important owing to its significant impact on communication and satellite signals. Therefore, the quiet-time morphology of EFI in each sector of the world (namely: American, African Asian and the Oceania) is discussed. The influence of geomagnetic storm activity on the occurrence pattern is also discussed.