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active region
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an area on the Sun where magnetic fields are concentrated; sunspots, prominences, flares, and CMEs all tend to occur in active regions
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aurora
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light radiated by atoms and ions in the ionosphere excited by charged particles from the Sun, mostly seen in the magnetic polar regions
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chromosphere
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the part of the solar atmosphere that lies immediately above the photospheric layers
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corona
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(of the Sun) the outer (hot) atmosphere of the Sun
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coronal hole
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a region in the Sun’s outer atmosphere that appears darker because there is less hot gas there
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coronal mass ejection (CME)
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a solar flare in which immense quantities of coronal material—mainly protons and electrons—is ejected at high speeds (500–1000 kilometers per second) into interplanetary space
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differential rotation
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the phenomenon that occurs when different parts of a rotating object rotate at different rates at different latitudes
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granulation
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the rice-grain-like structure of the solar photosphere; granulation is produced by upwelling currents of gas that are slightly hotter, and therefore brighter, than the surrounding regions, which are flowing downward into the Sun
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Maunder Minimum
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a period during the seventeenth century when the number of sunspots seen throughout the solar cycle was unusually low
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photosphere
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the region of the solar (or stellar) atmosphere from which continuous radiation escapes into space
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plage
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a bright region of the solar surface observed in the light of some spectral line
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plasma
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a hot ionized gas
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prominence
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a large, bright, gaseous feature that appears above the surface of the Sun and extends into the corona
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solar flare
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a sudden and temporary outburst of electromagnetic radiation from an extended region of the Sun’s surface
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solar wind
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a flow of hot, charged particles leaving the Sun
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sunspot
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large, dark features seen on the surface of the Sun caused by increased magnetic activity
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sunspot cycle
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the semiregular 11-year period with which the frequency of sunspots fluctuates
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transition region
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the region in the Sun’s atmosphere where the temperature rises very rapidly from the relatively low temperatures that characterize the chromosphere to the high temperatures of the corona