NASA's STEREO-B spacecraft is monitoring a vast hole in the sun's atmosphere--a "coronal hole." It's the dark region denoted by arrows in this extreme ultraviolet image taken during the early hours of Dec. 30th.

Coronal Hole
© SpaceWeather.com
Coronal holes are places in the sun's atmosphere where the solar magnetic field opens up and allows solar wind to escape. A stream of solar wind flowing from this coronal hole should reach Earth on Jan. 2nd or 3rd--the first solar wind stream of the New Year! High-latitude sky watchers should be alert for auroras.

.