We investigate the variation of the electric power density linked to VLF signals emitted by NWC transmitter. The power density measurements were detected by the Electric Field Detector (EFD) instrument onboard CSES satellite above NWC station and its conjugate region (CR). The beam is subject to disturbances and modulations in CR. Above the NWC station, the beam can be considered as a hollow cone with inconsistency dependence of the half-opening angle on the electric power density.

Scientists demystify stress changes before mainshocks and utilize the foreshocks as an indicator. We investigate changes in seismicity far from mainshocks by using tens of thousands of M ≥ 2 quakes for 10 years in Taiwan and Japan. The results show that wide areas exhibit increased seismicity occurring more than several times in areas of the fault rupture. The stressed crust triggers resonance at frequencies varying from ~ 5 × 10–4 to ~ 10–3 Hz that is supported by the resonant frequency model.

We use satellite data to analyze precursory anomalies of the western China Ms 7.1 Yushu earthquake by analyzing the signal-to-noise ratio (SNR) and using the full-wave model to illustrate a possible mechanism for how the anomalies occurred. The results show that very low-frequency (VLF) radio wave SNR in the ionosphere decreased before the Yushu earthquake. The full-wave simulation results confirm that electron density variation in the lower ionosphere will affect VLF radio signal SNR.

The CSES observed ionospheric Pc1 waves near the wave injection regions in conjugate hemispheres during the recovery phase of the geomagnetic storm on 27 August 2018. The Pc1s were found to be Alfvén waves with mixed polarisation propagating along background magnetic lines in the ionosphere. We suggest that the possible sources of Pc1 are EMIC waves generated near the plasmapause by the outward expansion of the plasmasphere into the ring current during the recovery phase of geomagnetic storms.

Identifying ionospheric disturbances associated with an earthquake is a useful and challenging work. A new decomposition and nonlinear fitting method has been developed to analyze ionospheric total electron content (TEC) data, and to extract disturbances that are likely related to Mw7.2 Mexico earthquake occurred on April 4, 2010. We found a unique TEC depletion that occurred around the epicenter on March 25, which cannot be explained by lower atmosphere wave or geomagnetic activity forcing.