Abstract

This paper is concerned with the properties of coronal mass ejections (CMEs) that aect the heliosphere. The special populations of CMEs that drive shocks, accelerate solar energetic particles, and produce geomagnetic storms are discussed in comparison with the general population (all CMEs of cycle 23). It is shown that the average CME speeds of the special populations are larger than that of the general population by a factor in the range 2–3. The angular width of these CMEs is also generally large because most of the CMEs were halos. The October – November 2003 period produced a large number of energetic CMEs, two of which were of historical proportions. These extreme events are discussed in order to understand what one might expect from the Sun as the largest event, given the maximum area and magnetic field strength of the source active regions.