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Last updated on April 20, 2014 at 1:20 EDT
UVCSEIT Composite Image of the Sun
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UVCS/EIT Composite Image of the Sun

March 31, 2003
The Sun's outer atmosphere a s it appears in ultraviolet light emitted by electrically charged oxygen flowing away from the Sun to form the solar wind (region outside black circle), and the disk of the Sun in light emitted by electrically charged iron at temperatures near two million degrees Celsius (region inside circle). This composite image taken by two instruments (UVCS, outer region and EIT, inner region) shows dark areas called coronal holes at the poles and across the disk of the Sun where the highest speed solar wind originates. UVCS has discovered that the oxygen atoms flowing out of these regions have extremely high energies corresponding to temperatures of over 200 million degrees Celsius and accelerate to supersonic outflow vel ocities within 1.5 solar radii of the solar surface. The structure of the corona is controlled by the Sun's magnetic field which forms the bright active regions and the ray-like structures originating in the coronal holes.