3D Coronal Hole (June 1, 2007)
The most distinctive feature on the Sun this past week has been a medium-sized coronal hole seen as the dark area in the lower right quadrant in this image from the STEREO (Ahead) spacecraft (May 25, 2007). When combined with an image taken by the Behind spacecraft, the image becomes 3D. Coronal holes appear darker in ultraviolet images, in this instance, in a spectral line of eleven-times ionized iron, formed at temperatures of about 1.5 million K.
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 several 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, which is the position we see here. 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.
SOHO began its Weekly Pick some time after sending a weekly image or video clip to the American Museum of Natural History (Rose Center) in New York City. There, the SOHO Weekly Pick is displayed with some annotations on a large plasma display.
If your institution would also like to receive the same Weekly Pick from us for display (usually in Photoshop or QuickTime format), please send your inquiry to firstname.lastname@example.org.