A pair of large coronal holes rotated into view over the past few days (Oct. 20-21, 2016). Coronal holes appear dark in certain wavelengths of extreme ultraviolet light, such as in the wavelength used here. These holes are areas of open magnetic field that spew solar wind into space. Sometimes, when they are facing Earth, they can cause geomagnetic disturbances that generate aurora. The lines you see were drawn to represent how solar scientists are modeling the magnetic field lines. Credit Solar Dynamics Observatory, NASA.
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