## Results
### Ionospheric Investigations
In particular, on 9 November 2022, offshore Pesaro Urbino town, a shallow (depth estimated equal to 5 km) Mw = 5.5 earthquake was recorded with epicentral coordinates 43.983\({}^{\circ}\)N, 13.324\({}^{\circ}\)E ([[http://cnt.rm.ingv.it/event/33301831](http://cnt.rm.ingv.it/event/33301831)]([http://cnt.rm.ingv.it/event/33301831](http://cnt.rm.ingv.it/event/33301831)), accessed on 28 January 2023). The anomaly depicted by Swarm Alpha in the geomagnetic field could have been induced by the aftershock activity recorded at the same coordinates, due to the compression of the two regional tectonic plates. Noticing that anomalous precipitation had been recorded on the same day (see Table 2 and Figure S7 in Supplementary Materials), we checked if there was evidence of lightning activity. We looked at the data from the Lightning Image Sensor (LIS) onboard the International Space Station (ISS) [43], acquired just one hour after the Swarm track above Italy, and presented this in Figure S32 in Supplementary Materials. There is no evidence of lightning activity in Italy, as it was detected only in Brazil \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline
**Swarm** & **Date** & **Time UT** & **Local Time** & **Anomalous Component** & **Dst [nT]** & **ap [nT]** & **F10.7 [SFU]** & **Figure** \\ \hline Bravo & 9 July 2022 & 19:25:45 & 20:19:32 & X-North, Y-East, Z-Center & \(-\)15 & 6 & 139.9 & Figure S9 \\ \hline Bravo & 10 July 2022 & 07:38:42 & 08:33:08 & X-North, Y-East, Z-Center & \(-\)6 & 9 & 155.3 & Figure S10 \\ \hline Bravo & 16 July 2022 & 18:51:07 & 19:43:40 & X-North, Y-East, Z-Center & \(-\)7 & 3 & 176.9 & Figure S11 \\ \hline Bravo & 17 July 2022 & 07:04:03 & 07:57:16 & X-North & \(-\)8 & 3 & 163.7 & Figure S12 \\ \hline Bravo & 31 July 2022 & 05:54:17 & 06:45:33 & Y-East & 14 & 5 & 95.1 & Figure S13 \\ \hline Bravo & 6 August 2022 & 17:06:22 & 17:56:06 & Y-East & 20 & 3 & 116.2 & Figure 9 \\ \hline Bravo & 14 August 2022 & 04:44:07 & 05:33:49 & X-North & \(-\)20 & 7 & 125.7 & Figure S14 \\ \hline Charlie & 26 August 2022 & 14:18:41 & 15:05:31 & Y-East & 1 & 4 & 120.4 & Figure S15 \\ \hline Alpha & 30 August 2022 & 13:53:05 & 14:46:46 & X-North & \(-\)4 & 7 & 124.4 & Figure S16 \\ \hline Charlie & 26 September 2022 & 11:19:43 & 12:19:28 & X-North, Y-East, Z-Center & 2 & 4 & 135.7 & Figure S17 \\ \hline Alpha & 3 October 2022 & 10:56:32 & 11:44:51 & Y-East & \(-\)11 & 5 & 158.3 & Figure S18 \\ \hline Charlie & 26 October 2022 & 08:42:02 & 09:38:43 & X-North & 10 & 0 & 122.8 & Figure S19 \\ \hline Alpha, Charlie & 13 November 2022 & 18:44:39 & 19:43:53 & X-North, Y-East, Z-Center & \(-\)8 & 6 & 136.1 & Figures 10 and S20 \\ \hline Alpha & 16 November 2022 & 18:46:36 & 19:27:45 & Y-East & 5 & 5 & 131.5 & Figure S21 \\ \hline Bravo & 8 December 2022 & 18:50:27 & 19:34:44 & X-North, Y-East & \(-\)14 & 7 & 142.3 & Figure S22 \\ \hline Alpha & 16 December 2022 & 15:54:40 & 16:47:10 & Y-East & \(-\)1 & 2 & 164.0 & Figure 11 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: List of the Swarm anomalous tracks in the circular research area of 235 km of radius centred on the ML3.3 Guidonia 1 January 2023 earthquake. and the Papua New Guinea region. We tend to exclude that a thunderstorm could have induced this Swarm anomaly, and that a seismo-induced origin is still plausible. Figure 11 shows a track of Swarm Bravo acquired during very quiet geomagnetic conditions (Dst = \(-\) 1 nT, ap = 2 nT), with an anomalous geomagnetic field Y-East component signal recorded above Central Italy. Though the track preceded by about one week the first shock of ML3.1 on 23 December 2022, and was acquired during the seismic acceleration phase, the diffuse nature of the anomaly makes it difficult to confirm that it could be seismo-induced, though that cannot be excluded. The analysis of electron density measured by Swarm Alpha, Bravo, and Charlie in the six months before the ML3.3 Guidonia 1 January 2023 earthquake is provided in supplementary materials.