Coronal Holes

There are no prominent coronal holes on the Earth-facing side of the Sun.

However, one or more sizable holes appear to be rotating into view over the Sun's eastern limb, as indicated in this Yohkoh soft x-ray image.

Coronal holes are regions where the corona is dark. These features were discovered when X-ray telescopes were first flown above the earth's atmosphere to reveal the structure of the corona across the solar disc. Coronal holes are associated with "open" magnetic field lines and are often found at the Sun's poles. The high-speed solar wind is known to originate in coronal holes.