## 6 Swarm Ne Disturbances during Nighttime of the 2016 Summer and Spring and M5+ Earthquakes  
In order to examine the sensitivity of LPs measuring onboard the Swarm constellation in different seasons of the year, two other seasons are selected, i.e., the summer solstice (May-July 2016) and the vernal equinox (February-April 2016). The Swarm data and earthquake data are selected using exactly the same rules as for the winter solstice season. Around 90 tracks from three months are selected--one for each nighttime. The region is the same as that in Figures 2a and 3a, and the same rules for latitudes, longitudes, and time  
Figure 9: The same as in Figure 7, but for the Aleutian Islands region, with tectonic plate boundary orthogonal to Swarm track at 55\({}^{\circ}\)N. Subfigure titles (**a**–**c**) refer directly to individual Swarm satellites. The earthquakes shown along the time axis have M \(\geq\) 5.0. The scales of Swarm Ne PSD maxima and cumulative sum of seismic energy are multiplied by 6 in comparison to Figures 7 and 8.  
have been applied. The starting reference track is always selected on the 17 th day of the middle month, and then around 90 tracks are matched with the starting one, depending on the Swarm orbit availability in the selected spatiotemporal windows. It should be mentioned that limited ranges of longitude and time could sometimes cause a loss of single tracks from the set, and this is visible as gaps in the blue lines of the average Swarm NE PSD in Figures 7-15. However, the gaps are always small and have no significance for the entire study. As mentioned in Section 3, the track selection in the summer and in the spring are not shown to save the space, and also because these sets have a similar spatial distribution to that from the winter. Figure 10 describes the summer case when a specific seismic activity level occurs. This level is lower in comparison to that from Figure 7, the number of earthquakes is smaller, and they only reach M = 6.4. Nevertheless, we can observe longer series around June 15-22 and shorter ones around July 25, when Dst does not indicate a storm, and the series occur instead in the phase of solar activity decrease. The second shorter series has indicated unconfirmed plasma bubbles at this time, but there are no plasma bubbles at the time of the first series. Both series of earthquakes coincide approximately with the largest Swarm A/C Ne disturbances at a 300 km wavelength (Figure 10a,c). There are smaller peaks of Swarm Ne PSDs that are precursory to the first earthquake series around June 9 in Swarm A/C, coinciding with increased geomagnetic activity, and the largest peak just is after the series (June 22), which happens at low ap/Dst indices. The other strong peaks of Swarm Ne PSDs are around July 16-19 (Swarm A and C), and the solar activity is also the strongest at that time. However, it should be noticed that at the time of the second earthquake group, which started around July 18-19, the solar activity increased in parallel to the seismic activity and Swarm disturbed signal occurrence. Swarm B also recorded disturbances at that time, and if we take a more detailed look at Figure 10b, we can easily find that all the small peaks from Swarm B coincide well with the seismic activity increase. Figure 11 describes the spring case, when, again, the seismic activity is lower than in the winter, and again includes specific increases in the form of earthquake groups. The maximum magnitude of an earthquake reaches 7.0 in this case. The most interesting epochs during these three spring months are the earthquake series that started around the beginning of April and lasted for almost three weeks and three very close-together and very shallow earthquakes on March 18. The longer earthquake series in April coincides with all other factors, i.e., the solar activity reaches the maximum at that time, ap 10-day average has a moderate increase here, as does Dst. Confirmed EPBs also occur on some days and coincide with the Swarm Ne PSD peaks.