The lithosphere-atmosphere-ionosphere coupling is a complex subject involving many physical effects and interactions that occur from the Earth surface up to the magnetosphere. The investigation of such coupling mechanisms – and in particular of the, partially unknown, behavior of the iono-magnetosphere transition region – is of fundamental importance for Earth remote sensing, monitoring of the near-Earth electromagnetic environment and studying of natural hazards. A great part of these effects is caused by natural non-seismic and anthropogenic electromagnetic emissions, but of particular relevance are the electromagnetic disturbances associated with the seismic activity that can produce ionospheric perturbations as well as the precipitation of particles from the Van Allen belts, observed before, during and after earthquakes of medium and strong magnitude. All of these phenomena must be distinguished from those induced by sources external to the geomagnetic cavity and by atmospheric events. In fact, an important role in controlling the dynamic of the topside ionosphere is played by the Sun – that generates (regular and irregular) variations of the lithosphere-ionosphere-magnetosphere parameters by impulsive events as solar Coronal Mass Ejections and Solar Flares – as well as by tropospheric activity (lightning, TLE, etc.)
Many experimental observations have been performed and theoretical models have been proposed in order to analyze and discriminate ionospheric disturbances caused by natural terrestrial events, such as earthquakes and volcanic eruptions, and by anthropogenic activities.
Seismicity is one of the consequence of the dynamic processes that take place in the Earth’s lithosphere. The study of the physical conditions which give rise to an earthquake, as well as of the processes that precede a seismic rupture, constitutes the basis of earthquake prediction approaches.
The objective of the CSES missions is to study the ionospheric disturbances induced by seismic activity and earthquake preparation mechanisms. It is based on long-term systematic and detailed measurements performed by detectors specifically designed. In particular, the missions aim at analyzing the temporal correlation between seismic events and occurrence of electromagnetic perturbations in the upper ionosphere and precipitations of Van Allen particles. Furthermore, CSES provides important information on ionosphere parameters and on the unknown behavior of the ionosphere-magnetosphere transition region, in order to develop physical models of the lithosphere-atmosphere-ionosphere coupling mechanism.