Holes in the Sun's Corona

This Solar Dynamics Observatory image of the Sun taken on January 10 in extreme ultraviolet light captures a dark coronal hole just about at sun center. Coronal holes are areas of the Sun's surface that are the source of open magnetic field lines that head way out into space. They are also the source regions of the fast solar wind, which is characterized by a relatively steady speed of approximately 800 km/s (about 1.8 million mph). As the sun continues to rotate, the high speed solar wind particles blowing from this hole will likely reach Earth in a few days and may spark some auroral activity.