Expansive coronal hole (September 21, 2007)
Hi-res TIF image (2.5M)
SOHO observed (September 19, 2007) a wide coronal hole that appeared as the large dark area when viewed in this wavelength (284 Angstrom) of extreme ultraviolet light (here) and in X-rays. It has been rotating around towards the center of the Sun over the past week or so. 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 almost the case here.
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. High-speed solar wind can have a direct effect on "space weather" near the earth. People living at the higher latitudes may be able to see some fairly colorful auroral displays in the next few days.
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.