7.2 Impact on frequency
Frequency of the perturbations are one of the crucial parameters to differentiate the perturbations induced by different sources. Hence, it is important to explore the frequencies of time varying inter-IPP distances along a satellite track. This will help to understand whether the band pass filter applied on ionospheric perturbation time series to filter the CIPs and TIPs also filters out the influence of inter-IPP distance or not. So, we transformed the time series of dTEC and inter-IPP distance pertaining to four satellite tracks (DGAR04, COCO07, HYDE11 and COCO23) from time domain to frequency domain. The time series and the corresponding periodograms are given in Fig.15. The periodograms of inter-IPP distances show that frequencies of the time varying inter-IPP distances are also lie within the frequency range corresponds to the acoustic and acoustic-gravity components (Fig. 15). It indicates that the unaccounted inter-IPP distances can be aliased as ionospheric perturbations and the band pass filters applied to filter the CIPs and TIPs cannot filter out the aliases cause by the unaccounted inter-IPP distances.