| Term: | Halo CME |
| Definition: |
A faint ring of enhanced emission seen around most or all of the edge of the occulting disk of a coronagraph. Indicative of a spatially large CME on the front side (Earthward) or back side of the Sun. The source region is usually nearer to solar central meridian than the limbs. Full halo CMEs from the front side of the Sun almost always result in geomagnetic storms at Earth, especially when accompanied by a solar proton event. |