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The Sun is not a quiet place, but one that exhibits sudden releases of energy. One of the most frequently observed events are solar flares: sudden, localized, transient increases in brightness that occur in active regions near sunspots. They are usually most easily seen in H-alpha and X-rays, but may have effects in the entire elecromagnetic spectrum. The X-ray brightness from a large flare often exceeds the X-ray output from the rest of the Sun. Another type of event, the coronal mass ejection, typically disrupt helmet streamers in the solar corona. As much as 1e13 (10,000,000,000,000) kilograms of material can be ejected into the solar wind. Coronal mass ejections propagate out in the solar wind, where they may encounter the Earth and influence geomagnetic activity. Coronal mass ejections are often (but not always) accompanied by prominence eruptions, where the cool, dense prominence material also erupts outward.
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