The Earth was bathed most of this last week in a solar stream that flowed out of this long coronal hole (image from December 27, 2005). Coronal holes appear as dark area of the corona when viewed in ultraviolet light and in X-rays (seen here traversing down the upper half of the Sun in ultraviolet light). This coronal hole area is one of the largest ones seen over the past year. Since coronal holes are 'open' magnetically, strong solar wind gusts can escape from them and carry solar particles out to our magnetosphere and beyond. Solar wind streams take 2 - 3 days to travel from the Sun to Earth, and the coronal holes in which they originate are more likely to affect Earth after they have rotated more than halfway around the visible hemisphere of the Sun. This same hole could reappear when the Sun rotates this area around again in about two weeks.

The magnetic field lines in a coronal hole open out into the solar wind rather than connecting to a nearby part of the Sun's surface. Coronal holes are responsible for the high-speed solar wind streams that sweep through the plane where the planets orbit -- and thus have a direct affect on "space weather" near the Earth. Transequatorial holes like this one affect the earth's magnetosphere directly. Thus, many people living at the higher latitudes probably experienced mild geo-effective storming for these few days in the form of aurora displays.