Coronal Mass Ejection

This chapter reviews the properties of Coronal Mass Ejections (CMEs) at the Sun and in the interplanetary medium. CMEs can eject between 1012and 1013kg of plasma from the Sun at speeds up to 2500 km/s. They are driven outwards by magnetic forces associated with the coronal magnetic field. In the interplanetary medium, they can have an organised magnetic structure and fast CMEs are often accompanied by strong shockwaves. In particular, periods of southward interplanetary magnetic field in excess of a few hours occur in CMEs and lead tomajor geomagnetic disturbances. © 2007 Springer-Verlag.