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.