The Sun was visually dominated by three substantial coronal holes that rotated across the face of the Sun this week (Sept. 8-10, 2015). Coronal holes are areas where the Sun's magnetic field is open and a source of streaming solar wind. They appear darker in extreme ultraviolet light because there is less material in the hole areas being imaged in this specific wavelength of light. It is a little unusual to have three coronal holes at the same time, but neither is it a rare occurrence. Credit: Solar Dynamics Observatory, NASA.
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