Swarm observations of ULF wave activity and plasma instability activity around extreme geophysical events

In November 2023, the ESA Swarm constellation mission celebrated 10 years in orbit, offering one of the best-ever surveys of the geomagnetic field and the topside ionosphere. Swarm provides an ideal platform for observing ultra-low frequency (ULF) waves and thus offers an excellent opportunity for space weather studies. For this purpose, a specialized time-frequency analysis (TFA) toolbox has been developed for deriving Pc1 (0.2-5 Hz) and Pc3 (20-100 MHz) wave indices, thus making it a useful tool for the study of magnetic storms. The TFA toolbox is also capable to identify in Swarm time series another category of natural-source electromagnetic signals, i.e., the post-sunset Equatorial Spread-F (ESF) events or plasma bubbles. There have been several studies suggesting that ULF pulsations may be associated with earthquakes. Previous studies refer mainly to the detection of these signals in ground-based magnetometer measurements. Besides, we note only a handful of studies that have been attempted to correlate ULF pulsations with seismic activity, using space-borne magnetometer measurements provided by Low Earth Orbit (LEO) satellites (e.g., CHAMP, DEMETER). Therefore, in this study we focus on the ULF pulsation and ESF activity observed by Swarm satellites during a time interval centered around the occurrence of the August 2016 Central Italy earthquake. Swarm has offered a variety of interesting observations around the time of this earthquake that could be associated with the occurrence of this extreme geophysical event.