Conference Agenda

Based on nighttime ELF wave power spectrum data acquired by the China Seismo-Electromagnetic Satellite (CSES), an improved method was developed to retrieve the D-region ionospheric reflection height from the ELF cutoff frequency. Through spectral trend extraction, noise suppression, and anomalous waveform screening, a global nighttime D-region reflection height dataset for 2019–2021 was constructed. By combining electron flux measurements from the energetic particle detector, X-ray count rates, and the retrieved reflection heights, the study revealed the physical process by which radiation-belt energetic electron precipitation enhances D-region ionization and lowers the reflection height. It quantitatively confirmed a significant positive correlation between electron flux and X-rays, and significant negative correlations between both of them and the reflection height, providing new observational evidence and technical support for understanding the influence of energetic particle precipitation on lower ionospheric structure.

For the significant atmosphere–ionosphere coupling disturbance triggered by the 15 January 2022 Hunga Tonga volcanic eruption, the ionospheric response was investigated using Japanese GEONET GNSS observations, Soratena barometric pressure measurements, and Swarm satellite electron density data. Two stages of ionospheric response were identified. The early stage was mainly characterized by concentric wave-like disturbances over the midlatitude region, consistent with Lamb-wave propagation, and had only a weak effect on GNSS positioning. The later stage showed much stronger ionospheric gradient enhancement at low latitudes, accompanied by meter-level PPP positioning errors. Swarm observations indicate that this later intense disturbance was closely related to eruption-triggered equatorial plasma bubbles. The study distinguished wave-driven and instability-driven responses, providing a basis for evaluating the impacts of volcanic events on ionospheric structure and navigation performance.

For earthquakes along the Chilean subduction zone, the characteristics of CID on the north and south sides of the epicenter were statistically analyzed. The results show that the relative amplitude characteristics of southward CID are generally consistent with those on the north side. Although the relative amplitude of southward CID is affected by the geomagnetic field, its propagation range is not constrained by it. Within 300–900 km south of the epicenter, the relative amplitude of CID is strongly influenced by the geomagnetic field, which in turn causes the relative amplitude associated with larger earthquakes to become smaller.

Taking the two eruptions of Sheveluch Volcano on 10 April 2023 and 17 August 2024 as case studies, their integrated characteristics were analyzed in conjunction with lithospheric seismic activity, atmospheric material transport, and thermal distribution. Significant differences were found between the two eruptions. The April 2023 eruption released 3692.8 kt of SO₂, with wider dispersion and longer residence time, whereas the August 2024 eruption released only 26.21 kt, reflecting clear differences in eruption dynamics and atmospheric transport patterns. SO₂ and the ultraviolet aerosol index showed significant responses to both eruptions, and the eruption column heights were about 10 km and 8–9 km, respectively. Positive temperature anomalies in the lower stratosphere were associated with the eruptions, while ozone depletion may have contributed to stratospheric cooling. The height of the tropopause during eruption may further amplify the effects in the lower stratosphere. These findings are of important significance for studies of sphere-coupling mechanisms.