Summary

The Sun’s magnetized plasma atmosphere is the source of various forms of activity, the most dramatic of which are coronal mass ejections (CMEs). These ejections are a bulk expulsion of plasma and magnetic field that travel out into the heliosphere, causing space weather effects on any planetary environments that they interact with. The origin of CMEs lies in the free magnetic energy stored in the coronal magnetic field, and a catastrophic evolution of the magnetic field structure that involves ideal or non-ideal magnetohydrodynamic processes or both.

The frequency of CMEs follows the 11-year solar activity cycle, indicating their origin in and near active regions at all evolutionary stages (i.e., from an active region’s emergence phase through the entirety of the decay phase). CMEs also originate in quiet sun filaments and coronal cavities. A particular magnetic field configuration known as a flux rope, which contains twisted magnetic fields and carries a volume current, is likely the key progenitor of CMEs.