SCINTILLATION SPECTRA INVESTIGATIONS DURING THE EVOLUTION OF IRREGULARITIES IN THE EQUATORIAL F REGION

Power spectra are calculated for the amplitude scintillation of VHFsignal at an equatorial station,Haikou.Theoretical simulation is also performed.Alot of set-ntillation events last for a long time.Temporal variation of amplitude scintillations arising due to the presence of irregularities in the night time equatorial Fregion is studied during the early and late stages of evolution of these irregularities.The higher frequency portion of the power spectra in the late stage are found to be steeper than these in the early stage.It can be attributed to the decay of irregularities with wavelength of several hundred meters in the late stage.The higher irregularity drift speed is found in the late phase.