For much of this week the sun featured three substantial coronal holes (Apr. 3-6, 2018). Coronal holes appear as large dark areas which are identified with arrows in the still image. These are areas of open magnetic field from which high speed solar wind rushes out into space. This wind, if it interacts with EarthÕs magnetosphere, can cause aurora to appear near the poles. They are not at all uncommon. Credit: Solar Dynamics Observatory, NASA.
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