This image from NASA’s Solar Dynamics Observatory on March 16, 2015, shows two dark spots, called coronal holes.
This image from NASA’s Solar Dynamics Observatory on March 16, 2015, shows two dark spots, called coronal holes. The lower coronal hole was one of the biggest observed in decades. Coronal holes can be the source of the fast solar wind. The magnetic field in these regions extends far out into space rather than quickly looping back into the sun’s surface. Credit: NASA/SDO