CORONAL HOLE: A dark hole has formed in the sun’s atmosphere. NASA’s STEREO-B spacecraft photographed it just hours ago:
It’s a “coronal hole,” a vast region where solar magnetic fields have opened up and allowed some of the sun’s atmosphere to escape. The runaway atmosphere is heading our way in the form of a solar wind stream. High-latitude sky watchers should be alert for auroras when it arrives on or about May 3rd.