2.2 Angular width
The angular width of CMEs projected in the plane of the sky ranges widely from 2° to
360° (Yashiro et al., 2004), with a significant fraction in the low end (e.g., < 20°) and a small fraction in
the high end (e.g., > 120°). The CMEs with the angular width less than 10° can be called narrow
CMEs (Wang et al., 1998), and others are sometimes called normal CMEs (Yashiro et al., 2004, see
Figure 1). Note that halo CMEs, with an apparent angular width of or close to 360°, are simply due to that
the CMEs, probably with an angular width of tens of degrees, propagate near the Sun-Earth line, either
toward or away from the Earth.