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An outward eruption into interplanetary space of material from the solar corona. CMEs are associated with features in the Sun's magnetic field. During periods of high solar activity, one or two occur each day, originating over a broad range of solar latitude. In periods when the Sun is quiet, they occur less frequently (around once every 3-10 days), and are confined to lower latitudes. The average ejection speed ranges from 200 km/s at minimum activity to twice that speed at solar maximum. Most occur without an accompanying flare; if a flare does occur, it usually follows the onset of the CME. They are the most energetic of all transient solar phenomena and have a marked effect on the solar wind. Large CMEs in the plane of the Earths orbit are responsible for geomagnetic storms.
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