STEREO - Solar Terrestrial Relations Observatory
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Important notice about STEREO Behind

Active Region in Profile

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The STEREO (Behind) spacecraft caught the billowing arcs of a new active region in profile as it came around the limb of the Sun (July 23, 2009). It can see this before anyone else from its perspective trailing behind Earth (generally along Earth’s orbital path), The graceful twisting and looping arcs of the region are actually particles spiraling along magnetic field lines emerging from the active region as viewed in the 171 Angstrom wavelength of extreme UV light. Without any warning, the region blew a cloud of particles out into space with a small coronal mass ejection (CME). Although the eruption is not easy to pick out in the still, the faint burst is easy to spot in the video clip. The longer video clip shows most of the Sun for a two and a half day period as the region emerges and includes the small CME near the end.


Last Revised: March 19, 2018 15:00:39 UTC
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