## 1 Introduction
[47] have prepared a statistical spatiotemporal analysis of CSES-observed disturbed ionospheric signals due to an earthquake occurrence, which is quite analogous to the analyses made with Swarm data in [48]. [PERSON] et al. [49] significantly extended the analyses of Swarm Ne disturbances in relation to seismic activity. They analyzed the global distribution of Swarm Ne disturbances and compared them to areas of higher and lower seismic activity rather than to specific earthquakes. Their analysis has a commonality with our current study, as we also try to focus on the continuous global seismic activity of various magnitudes. They analyzed global Ne disturbances statistically, with no spectral tools. In contrast, we try to analyze one important place locally and decompose disturbances in their frequency domain. The advantage of LEO satellites is that they provide data in places that cannot be reached by ground GNSS observations. The orbital tracks of LEO can reach all seismically active zones of the world. A drawback of LEO is that the satellite data are dense only along the orbital tracks. The one-dimensional nature of LEO along-track Ne observations and sometimes the limited chance for spatiotemporal correlation due to the nonrepeating orbits leads to a strong requirement for spectral analysis for better recognition of the signals. The spectral analysis of residual signals can be found several times in the studies on seismically induced ionospheric disturbances in ground GNSS data [17; 18; 50]. It is possible that the processing of LEO data requires a spectral approach more than time series from a ground station do, as the disturbed signal is less pronounced in transient LEO observations. Fortunately, the frequency domain has been analyzed more frequently in LEO data in recent years [35; 51; 52; 53; 54]. These studies are encouraging us to take a further step and try a spectral classification of specific patterns that refer to different Ne and TEC signal disturbances. The proposed research aims at the investigation of LAIC via short-term Fourier transform (STFT) analysis of disturbed Ne, measured by Swarm over tectonic plate boundaries. This facilitates the analysis of seismically induced ionospheric disturbances with respect to larger earthquakes and their groups within the earthquake catalogue. The validation of disturbances detected by Swarm satellites in times of strong earthquake activity is based on the analysis of analogous data from the periods and places of lower seismic activity. The spectral decomposition of the disturbed signal can significantly help in the inspection of spectral behavior of ionosphere anomalies and the identification of the most frequent wavelengths of their occurrence. These determined spectral patterns, after more extended research in the future, can be classified as different types of disturbed signals, which was previously suggested in [17; 18; 51; 52]. The extended spectral analyses of LEO electric field data can, in the future, help in the recognition of satellite data disturbances related to different seismic activities like mainshocks, aftershocks, preseismic activity, and also to moderate seismic activity in the vicinity of tectonic boundaries. The tectonic plate boundaries are weak places of the Earth's lithosphere and can trigger preseismic, co-seismic, and post-seismic ionospheric disturbances. Swarm satellites visit these boundaries at different longitudes on the subsequent days and, due to their high speed, collect short samples of observations along their orbits. Therefore, the current study investigates two issues: firstly, a comparison of three-month-long records of Ne disturbances to the continuous seismic activity and not only to the largest earthquakes; secondly, a preliminary STFT recognition of Swarm Ne disturbances. In both cases, Swarm-derived Ne are compared with continuous seismic records acquired from the United States Geological Survey (USGS) in the regions of interest.