source's Nasa - NOAA - SWPC
This channel shows the features that our eyes would see if we dim the Sun's intensely bright light. This wavelength of light is visible to people as blue-indigo, although here it is shown in yellow. Sunspots stand out sharply here, and you can also see that the edge of the Sun appears darker � a well-known effect called limb darkening.
Wavelength: 4500 angstroms (0.00000045 m) = Visible (blue-indigo)
Primary ions seen: Continuum
Characteristic temperature: 6,000 K (11,000 F)
This channel is especially good at showing areas where cooler dense plumes of plasma (filaments and prominences) are located above the visible surface of the Sun. Many of these features either can't be seen or appear as dark lines in the other channels. The bright areas show places where the plasma has a high density.
Where: Upper chromosphere and lower transition region
Wavelength: 304 angstroms (0.0000000304 m) = Extreme Ultraviolet
Primary ions seen: singly ionized helium (He II)
Characteristic temperature: 50,000 K (90,000 F)
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