Mass acceleration processes: The case of the coronal mass ejection

Abstract

A theoretical review is given on what drives the coronal mass ejection, centering on the question of the origin of its total energy, typically of the order of a few 10 31 erg. This energy accounts for the work of lifting and accelerating the ejected mass as well as a significant amount left in the open magnetic field created by the ejection. It is pointed out that the total energy cannot be stored in the pre-eruption corona entirely in the form of force-free electric currents, based on a plausible magnetohydrodynamic conjecture of Aly. Storage in the form of cross-field electric currents held in equilibrium by pressure and gravitational forces seems possible, in particular if these currents are associated with closed magnetic fluxes entirely detached from the atmospheric base. The implications and physical issues of these results for the mass ejection are discussed, leading to several suggestions for future study.