A Pc3 magnetic pulsation possibly associated with the Lamb wave generated by the 2022 Tonga undersea volcanic eruption

A peculiar compressional Pc3 magnetic pulsation was observed by the Swarm satellites on the dayside which may have been caused by the Lamb wave generated at the Tonga undersea volcanic eruption on January 15, 2022. The difference between this and other usual compressional Pc3 pulsations observed at low and mid-latitudes is its spectral structure. The power spectral density (PSD) usually peaks at the periods between 20 and 30 sec, but in this event observed on the dayside orbit around the time when the Lamb wave passed under the Swarm orbit, the PSD peaks below 20 sec and is small in the periods longer than 20 sec. It is shown that this is a very rare case, although not the only one, during the period examined, i.e., from December 2013 to April 2022. The PSD has many sharp spectral peaks, but they don't have usual harmonic structure, and the frequencies of the peaks are nearly common with those of other similar events. The Pc3s observed at low-latitude (L<3 Re) ground magnetic stations simultaneously with the satellites show a very good correspondence of PSD peaks with those of the Swarm satellites although those of high-latitude station do not. The solar wind on January 15, 2022 was disturbed and high speed, so the possibility that the solar wind was the cause of the Pc3 cannot be completely excluded. However, the coincidence of the Pc3 appearance with the Lamb wave arrival, its peculiar spectral structure, and a comparison with ground magnetic observations suggest that this phenomenon is likely to be related to the Lamb wave arrival. A plasmaspheric cavity resonance excited by a magneto-sonic wave injected from the ionosphere via ionospheric dynamo could be a possible mechanism. This is probably the first report on a Pc3 magnetic pulsation possibly caused by lower atmospheric disturbance.