Solar Flares and Coronal Mass Ejections

Introduction Solar flares and coronal mass ejections (CMEs) comprise a huge topic, encompassing most subdisciplines of solar physics. Observations of flares and CMEs have been summarised in Section 1.9, but more comprehensive accounts can be found in Hudson (2010) and Moore et al. (2011). The present chapter simply focuses on the main MHD aspects of two-ribbon flares and CMEs. These include initiation of the eruptive process responsible for most major events (Sec. 12.2), and the MHD of energy release by reconnection (Sec. 12.3) (see also, e.g., Priest and Forbes 2002; Forbes 2010; Chen 2011; Shibata and Magara 2011). Non-eruptive simple-loop flares (e.g., Priest 1981) and particle acceleration (e.g., Miller et al. 1997; Birn and Priest 2007) are not addressed, even though they are important; indeed, the presence of up to 50 per cent of the energy in some flares in the form of fast particles is at present a major puzzle. O verview A prominence may slowly evolve for days or months before reaching a critical point and suddenly erupting into interplanetary space over a few minutes or hours (Figure 1.37). Along with the prominence eruption, a large overlying coronal structure erupts as a CME, often having the appearance of Figures 1.38a and 12.1a with the prominence at its core. This three-part structure is observed in the solar wind as an interplanetary CME consisting of a shock wave, magnetic cloud and prominence material.