Pc3 geomagnetic pulsations excited by earthquakes and their commonality with solar wind-originated Pc3

The source of compressional Pc3 magnetic pulsations has been considered to be the plasma process in the solar wind or in the magnetosphere. However, we found some strong inland earthquakes that occur on the dayside also excite Pc3s. The Lamb waves generated by the January 2022 Tongan undersea volcanic eruption are also believed to have excited large amplitude and short period compressional Pc3 geomagnetic pulsations in the dayside plasmasphere (Iyemori et al., 2025). Increases in power spectral density (PSD) in the Pc3 frequency band were observed 10-30 minutes after the origin time of large inland earthquakes (M>6.5) during the daytime (10-14 LT). During these large earthquakes, seismic waves with period of 10-30 seconds propagate far away (even more than several thousand km), causing slight fluctuations in the orientation of magnetometer sensors, resulting in apparent Pc3-like fluctuations. To avoid such sensor tremor effect, we analyzed the total force of magnetic field, or analyzed comparing with seismometer data. We also used the Swarm satellite observation. The PSD of Pc3s caused by earthquakes or by Lamb wave show many spectral peaks having interval of 3-5 mHz, and this is similar with the characteristic reported by, for example, Samson et al. (1995) for normal, i.e., solar wind origin Pc3s. In this paper, we will also show the commonality between the Pc3s caused by earthquakes or Lamb waves and those originated from the solar wind and discuss what the commonality means.