Earth-pointing coronal hole - January 30, 2008

A substantial coronal hole can be seen (below center and extending to the right) in this February 9, 2008 image by STEREO (Behind). Coronal holes appear as darker areas when viewed in this extreme UV wavelength (195 Angstroms). With the angle of this image coming from behind Earth's orbit, the coronal hole is actually further to the left when viewed from Earth. Solar wind from coronal holes that are observed to the right of the Sun's central line connects best with Earth. Since coronal holes are 'open' magnetically, strong solar wind gusts escape from them and carry solar particles out to our magnetosphere and beyond. Solar wind streams take several days to travel from the Sun to Earth.

The magnetic field lines in a coronal hole open out into the solar wind rather than connecting to a nearby part of the Sun's surface. High-speed solar wind can have a direct effect on "space weather" near Earth. People living at the higher latitudes have already seen some colorful auroral displays which could continue for a few more days.

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