Coronal Mass Ejection - An eruption in the outer solar atmosphere that sends billions of tons of magnetized plasma clouds into interplanetary space. When traveling at high speeds these ejections creat
e shocks in the solar wind. Earth-intercept of a CME is often followed by a geomagnetic storm
Half the full angular width of the CME, which is a measure of the size of a coronal mass ejection as it propagates away from the Sun. Often the propagation is assumed to sweep out the shape of a cone
in interplanetary space. The angle between the cone edge and the central axis of the cone is the opening half-angle
The speed of a CME that is transverse to the Sun-observer line. This speed is always an underestimate of the CME speed since it does not include the radial motion (to/from observer)