Study on the occurrence characteristics of VHF and L-band ionospheric scintillations over East Africa

Abstract

A study of the occurrence of ionospheric scintillations at the VHF and L-band frequencies was carried out at an East African station, with geographic coordinates: UoN (Lat: 1.3^o S; Lon: 36.8^o E) and Mak (Lat:0.3^o N; Lon:32.5^o E) during 2011 and 2012, respectively. Observations were made for the nighttime period starting from 6 pm to 6 am local time, the following day. It was found that pre-sunset scintillations were more frequent from January to March, and after the March equinox, the onset times quickly shifted to pre-midnight and lasted up to pre-dawn hours. The co-existence of both the VHF and L-band frequency scintillations was also observed, but the small scale irregularities responsible for the L-band scintillations could not exist beyond local midnight. Of particular interest were the VHF scintillations signatures at the onset, which were highly structured in short duration patches, but having longer durations with reduction in intensity as time progressed. This was attributed to the higher F-region zonal drift speed of irregularities at the onset, which reduced with time.