A new hole is opening in the sun’s atmosphere, and it is spewing a stream of solar wind into space. This extreme ultraviolet image from NASA’s Solar Dynamics Observatory shows the opening, which stretches more than 600,000 km from top to bottom:
Researchers call this a “coronal hole”–a region where the sun’s magnetic field opens up and allows solar wind to escape. Why is the hole dark? Because much of the hot glowing gas that used to be there is gone.
Solar wind flowing from this hole is expected to reach Earth on April 20th. G1-class geomagnetic storms and high-latitude auroras are possible at that time. Sky watchers between 50o and 60o N latitude should also be alert for STEVE, which tends to appear in that latitude range during springtime geomagnetic storms. Free: Aurora Alerts