chromosphere

Part of the outer gaseous layers of the Sun (and other stars), a few thousand km deep. It is visible as a thin crescent of pinkish light during a total eclipse of the Sun.

The chromosphere (literally, "color sphere") is a thin layer of the Sun's atmosphere just above the photosphere, roughly 10,000 kilometers deep (approximating to, if a little less than, the diameter of the Earth). The coloration may be seen directly with the naked eye only during a total solar eclipse, where the chromosphere is briefly visible as a flash of color just as the visible edge of the photosphere disappears behind the Moon.

Without special equipment the chromosphere cannot normally be seen due to its being washed out by the overwhelming brightness of the photosphere.

The most common solar feature within the chromosphere are Spicules, long thin fingers of luminous gas which appear like the blades of a huge field of fiery grass growing upwards from the photosphere below.

Another feature found in the chromosphere are fibrils, horizontal wisps of gas similar in extent to spicules but with about twice the duration.

Finally, solar prominences rise up through the chromosphere from the photosphere, sometimes reaching altitudes of 150,000 kilometers.

Above the chromosphere of some stars there is a so-called transition region, where the temperature increases rapidly to the hot corona, which forms the outermost part of the atmosphere.

See the flash spectrum of the solar chromosphere (Eclipse of March 7th, 1970).