via National Geographic Photo of the Day http://photography.nationalgeographic.com/photography/photo-of-the-day/koolau-summit-hawaii-ngpc2015/
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Wednesday, October 14, 2015
NASA Coronal Hole Front and Center
The dark area across the top of the sun in this image is a coronal hole, a region on the sun where the magnetic field is open to interplanetary space. via NASA http://www.nasa.gov/image-feature/goddard/coronal-hole-front-and-center