Coronal mass ejection
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A coronal mass ejection (CME) is an unusually large release of plasma and magnetic field from the solar corona. They often follow solar flares and are normally present during a solar prominence eruption. The plasma is released into the solar wind, and can be observed in coronagraph imagery.
Coronal mass ejections are often associated with other forms of solar activity, 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 planetary system, or beyond (interplanetary CME). The ejected material is a plasma consisting primarily of electrons and protons. While solar flares are very fast, CMEs are relatively slow.
Coronal mass ejections are associated with enormous changes and disturbances in the coronal magnetic field. They are usually observed with a white-light coronagraph.
Recent scientific research has shown that the phenomenon of magnetic reconnection is closely associated with CMEs and solar flares. In magnetohydrodynamic theory, the sudden rearrangement of magnetic field lines when two oppositely directed magnetic fields are brought together is called "magnetic reconnection". Reconnection releases energy stored in the original stressed magnetic fields. These magnetic field lines can become twisted in a helical structure, with a 'right-hand twist' or a 'left hand twist'. As the Sun's magnetic field lines become more and more twisted, CMEs appear to be a 'valve' to release the magnetic energy being built up, as evidenced by the helical structure of CMEs, that would otherwise renew itself continuously each solar cycle and eventually rip the Sun apart.
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