A coronal mass ejection (CME) is a massive burst of gas and magnetic field arising from the solar corona and being released into the solar wind, as observed in a coronagraph.
Coronal mass ejections are often associated with other forms of solar activity, most notably solar flares or filament eruptions, but a broadly accepted theoretical understanding of these relationships has not been established. CMEs most often originate from active regions on the Sun's surface, such as groupings of sunspots associated with frequent flares. Near solar maxima, the Sun produces about three CMEs every day, whereas near solar minima, there is about one CME every five days.
Coronal mass ejections release huge quantities of matter and electromagnetic radiation into space above the sun's surface, either near the corona (sometimes called a solar prominence), or farther into the planet system, or beyond (interplanetary CME). The ejected material is a plasma consisting primarily of electrons and protons.
Coronal mass ejections are associated with enormous changes and disturbances in the coronal magnetic field. They are usually observed with a white-light coronagraph.