## 6 Swarm Ne Disturbances during Nighttime of the 2016 Summer and Spring and M5+ Earthquakes
Therefore, in April 2016, it is hard to credibly assess the reason for the very high Swarm Ne PSD peaks, but at the same time, a seismic source is hard to exclude. Additionally, if we take a look at two slightly smaller, but still considered large, Swarm Ne PSD peaks in Figure 11a (March 19 and April 6), we can see that F10.7 is not high at that time, the ap and Dst are low or moderate, but groups of shallow earthquakes are very close to Swarm disturbances. Summarizing Figure 11, we can say that there are more cases of large Swarm Ne PSDs at 300 km that coincide with some characteristic seismic activity than those coinciding closely with the highest average ap, particularly anomalous Dst or solar radio flux. Figure 10: The same as in Figure 7, but for the summer of 2016. Subfigure titles (a–c) refer directly to individual Swarm satellites. Swarm Ne Disturbances during Daytime of the 2016-2017 Winter and Daytime of the 2016 Summer and Spring and M5+ Earthquakes  
The selection of Swarm trajectory parts in Sections 4-6 was focused on the evening or night hours, which was motivated by the severe observational conditions during the day. Indeed, it will be shown that the sensitivity of Swarm to Ne differs in the daytime. This section investigates daytime Swarm tracks, which, as in the former sections, can differ by some hours between the Swarm A/C pair and Swarm B due to the constellation geometry. However, each Swarm spacecraft visits the same region twice daily (one ascending and one descending track), and it is possible to find the passes closer to midnight, as well as those closer to noon. The Swarm Ne PSD sampled at a 300 km wavelength from the daytime  
Figure 11: The same as in Figure 7, but for the spring of 2016. Subfigure titles (**a–c**) refer directly to individual Swarm satellites. spectrograms in the winter of 2016-2017 is presented in Figure 12. The Swarm Ne PSD at 300 km has a significantly smaller amplitude in the daytime, which is shown by low values of light-blue area plots and bold blue lines. It can, however, be concluded from the entire Figure 12 that Swarm LP signals at a 300 km wavelength have a small amplitude and poorly coincide with the earthquakes, as well as with the average ap, Dst, or F10.7 series. The only conclusion with regard to the Swarm A/C pair (Figure 12a,c) is that among the Swarm disturbances in the daytime, at most, some low precursory signals can be found, rather than co-seismic ones. This small sensitivity of Swarm LPs at a 300 km wavelength during sunny conditions encouraged us to inspect the shorter wavelengths, which have, however, much lower amplitudes of the signal. The sampling of Swarm Ne PSDs at higher frequencies provided some interesting findings, which appeared worth presenting and are therefore shown in Figures 13-15. Swarm orbital track samples are selected for the same three analyzed seasons in the daytime, and the calculated STFT spectrograms are sampled at a very short wavelength of 80 km, corresponding to around 10 s of Swarm flight. The signals have significantly smaller amplitudes at a 80 km wavelength, and therefore, the scale of the Swarm Ne PSD and its 10-day average presented in Figures 13-15 is increased a hundred times in comparison to the case of signals sampled at a 300 km wavelength in Figures 7, 8 and 10-12. Figure 13 presents some peaks of the Swarm Ne PSD, but their time location differs between the satellites. Figure 13a for Swarm A in the winter daytime shows one peak of Ne signal at 80 km, around November 25. This is the time of relaxation from earthquakes with M \(\geq\) 5.0, and it is possible that a higher ap and larger negative Dst contribute to that disturbance. On the other hand, there is a second peak at the beginning of December, which coincides exactly with a shallow earthquake at the time of a low ap and Dst around zero. These two peaks raise the 10-day moving average of the Swarm Ne PSD in such a way that it looks like a precursor to the earthquake series.