CORONAL HOLE: NASA’s Solar Dynamics Observatory is monitoring a coronal hole in the sun’s northern hemisphere. It is the UV-dark region in this image taken during the early hours of Sept. 21st:

The white lines in the image trace the sun’s magnetic field. A coronal hole is a place where the magnetic field spreads apart, allowing solar wind to escape. A stream of solar wind flowing from this particular coronal hole is heading for Earth, due to arrive on Sept. 23-24. Its arrival could add to the impact of a minor CME expected to reach Earth at about the same time. Polar geomagnetic storms are possible early next week.

fr/spaceweather.com