Les éjections de masse coronale et après? Un aperçu de leur impact sur l'environnement terrestre et planétaire

The Sun’s activity exhibits a variety of transient phenomena which interact with the ambient solar wind and affect its global structure. In addition, they may impinge on Earth and on the planets of the solar system and modify their environment. The effects of solar events on the geospace and more generally in the heliosphere is one the questions that will be addressed by the mission Solar Orbiter, scheduled for launch in 2018, and combining remote sensing and in situ observations.

I will focus on Coronal Mass Ejections (CME) and on their consequences in the magnetosphere such as the triggering of major events or magnetic storms. Particularly intense events are known to damage electric equipments on spacecraft, disturb GPS communications, and even induce currents in power grids on the ground, causing severe breakdowns. However, our capability to predict the geoeffectivity of these events remains poor. I will start with an overview of the chain of processes that affect both CMEs and the local medium on their way from Sun to Earth. I will highlight results inferred from in situ measurements in two aspects: propagation in the interplanetary medium and impact on planets. I will show in particular the role of the external boundaries of the terrestrial environment. And finally, I will discuss the effects of CMEs on other planets.