No Big Deal, Just a Giant Hole in the Sun

Coronal holes are areas on the sun's corona that are darker, lower-density, and (relatively) colder than the rest of the plasma on the surface of our nearest star. They're the source of the kind of solar wind gusts that carry solar particles out to our magnetosphere and beyond, causing auroras (and, less awesomely, geomagnetic storms) here on Earth.
No Big Deal, Just a Giant Hole in the Sun