1 Introduction

Coronal mass ejections (CMEs) are spectacular eruptions in the solar atmosphere. They originate from coronal-loop-sized scale (∼ 104 km), expand to cover a significant part of the solar surface, and further extend all the way from the low corona to the interplanetary space, through which they become the largest-scale eruptive phenomenon in the solar system. Similar phenomenon was also identified on other stars (Collier Cameron and Robinson, 1989). During their propagation in the solar system, CMEs may frequently interact with the Earth (and other planets), producing a series of impacts on the terrestrial environment and the human high-tech activities (see Schwenn, 2006Jump To The Next Citation Point; Pulkkinen, 2007, and references therein). Although CMEs may have been caught a glimpse during the occasional total solar eclipses in the past thousands of years, and have been inferred in the early 20th century (see Cliver, 1995; Alexander et al., 2006, for reviews) as an eruptive phenomena, they were discovered by the coronagraph on board the seventh Orbiting Solar Observatory (OSO-7) satellite on 1971 December 14 (Tousey, 1973), which was 112 years after the first observation of solar flares. Such a delay resulted in many controversies in identifying the source of various shock wave-related phenomena, e.g., type II radio bursts, Moreton waves, and EIT waves1 (Vršnak and Cliver, 2008Jump To The Next Citation Point), as well as the source of the ensuring space weather disturbances (Gosling, 1993). On the other hand, the understanding of CMEs benefits significantly from the earlier developed models for solar flares, as well as filament eruptions (see Priest and Forbes, 2002, for a review on solar flares).

A lot of CME-related models have been developed to describe their pre-eruption structures (hereafter called progenitors), their initiations, and their eruptions. It is found that from time to time these models, which describe different phases of the CMEs, were lumped together in the literature. In this paper, we try to separate them into different subsections in order to distinguish their applications to different stages of CMEs, which may be biased toward my personal viewpoints though. For more reviews on CME models, the readers are referred to Klimchuk (2001), Zhang and Low (2005), Forbes (2000Jump To The Next Citation Point), Forbes et al. (2006Jump To The Next Citation Point), and Vršnak (2008).

In this paper, we start with the brief description of the observational features of CMEs in Section 2, and various CME models are reviewed in Section 3, where the subsections are devoted to the models for their pre-eruption, initiation, and eruption stages. In Section 4, we present several topics that are under strong controversy or remain elusive, which are followed by a summary in Section 5.

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