Occurrence statistics of Spread F at Ilorin

Abstract

This study is the first of its kind aimed at the statistical study of the occurrence of Equatorial Spread-F (ESF) using ionosonde data obtained with the aid of Digisonde (DPS-4) during the year 2010 at Ilorin (Geo. Lat. 8.47⁰N, Long. 4.68⁰E, and Dip. Lat. 7.867⁰S): an equatorial station in the African sector. The study revealed that the ionosphere over Ilorin exhibit three types of equatorial spread-F i.e. frequency spread F (FSF), range spread F (RSF) and mixed frequency (MSF). ESF is observed to be a post-sunset and nighttime phenomenon; occurring within the hours of 2000LT and 0700LT with the range of hmF2 being between 230 and 405 km. ESF grows during the post-sunset periods and decays towards the sunrise hour. ESF is observed to be monthly/seasonal dependent. Occurrence of ESF is observed to be predominant during the equinox months. The results further show that RSF type is the most prevalent at this station.