Ionospheric scintillations are rapid variations of phase and amplitude of a signal, which passes through the ionosphere. They are very pronounced in equatorial regions where they appear every day after sunset and may last for a few hours. They are related in particular to solar activity and the season. The main factors whose dependency has been established are indicated hereafter. At midlatitudes, the scintillations are rather weak, except during conditions of ionospheric storms. Very strong effects relating to storms can be observed in the auroral regions.
ITU-R REPORT P.2097-2007 history
2007ITU-R REPORT P.2097-2007 Transionospheric radio propagation The Global Ionospheric Scintillation Model (GISM)