Jan 23, 2013 - Why NASA Scientists Observe the Sun in Different Wavelengths
Taking a photo of the sun with a standard camera will provide a familiar image: a yellowish, featureless disk, perhaps colored a bit more red when near the horizon since the light must travel through more of Earth's atmosphere and consequently loses blue wavelengths before getting to the camera's lens.
The sun, in fact, emits light in all colors, but since yellow is the brightest wavelength from the sun, that is the color we see with our naked eye -- which the camera represents, since one should never look directly at the sun. When all the visible colors are summed together, scientists call this "white light."
snip:
Each wavelength was chosen to highlight a particular part of the sun's atmosphere.
From the sun's surface on out, the wavelengths SDO observes, measured in Angstroms, are:
+ 4500: Showing the sun's surface or photosphere.
+ 1700: Shows surface of the sun, as well as a layer of the sun's atmosphere called the chromosphere, which lies just above the photosphere and is where the temperature begins rising.
+ 1600: Shows a mixture between the upper photosphere and what's called the transition region, a region between the chromosphere and the upper most layer of the sun's atmosphere called the corona. The transition region is where the temperature rapidly rises.
+ 304: This light is emitted from the chromosphere and transition region.
+ 171: This wavelength shows the sun's atmosphere, or corona, when it's quiet. It also shows giant magnetic arcs known as coronal loops.
+ 193: Shows a slightly hotter region of the corona, and also the much hotter material of a solar flare.
+ 211: This wavelength shows hotter, magnetically active regions in the sun's corona.
+ 335: This wavelength also shows hotter, magnetically active regions in the corona.
+ 94: This highlights regions of the corona during a solar flare.
+ 131: The hottest material in a flare.
The complete article is here: [link to www.spacedaily.com]