Green Arches (December 10, 2004)
Hi-res TIF (1.3M)
As an active region approached the edge of the Sun, its many towering
arches became visible (at least for SOHO) for several days (Dec. 4 - 6,
2004). The subtle structures are fine and web-like as they gracefully
shift and sway above the bright active region. It is hard to believe
that these loops rise above the Sun to a height many times the size of
What are they? The gas in the Sun's outer atmosphere is so hot that collisions among the atoms strip off most of the electrons -- creating a gas of positively charged ions and negatively charged electrons, known as a plasma. Electromagnetic forces make it difficult for charged particles to cross magnetic field lines; instead, the plasma is trapped in tubes of magnetic flux, and the bright regions show us where there's both lots of plasma and a strong magnetic field. The green color is just a tone added to the black and white images to make it easier to tell what specific wavelength of light an imager is observing.
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.