Early life of coronal mass ejections

Coronal mass ejections (CMEs) are large-scale magnetized plasma structures ejected from closed magnetic field regions of the Sun. White light coronagr aphic observations from ground and space have provided extensive informatio n on CMEs in the outer corona. However, our understanding of the solar orig in and early life of CMEs is still in an elementary stage because of lack o f adequate observations. Recent space missions such as Yohkoh and Solar and Heliospheric Observatory (SOHO), and ground-based radioheliographs at Nobe yama and Nancay have accumulated a wealth of information on the manifestati ons of CMEs near the solar surface. We review some of these observations in an attempt to relate them to what we already know about CMEs. Our discussi on relies heavily on non-coronagraphic data combined with coronagraphic dat a. Specifically, we discuss the following aspects of CMEs: (i) coronal dimm ing and global disk signatures, (ii) non-radial propagation during the earl y phase, (iii) Photospheric magnetic field changes during CMEs, and (iv) ac celeration of fast CMEs. The relative positions and evolution of coronal di mming, arcade formation, prominence eruption will be discussed using specif ic events. The magnitude and spatial extent of CME acceleration may be an i mportant parameter that distinguishes fast and slow CMEs. (C) 2000 Elsevier Science Ltd. All rights reserved.