Source : Webster's Revised Unabridged Dictionary (1913)

Chromosphere \Chro"mo*sphere\, n. [Gr. ? color + E. sphere.]
   (Astron.)
   An atmosphere of rare matter, composed principally of
   incandescent hydrogen gas, surrounding the sun and enveloping
   the photosphere. Portions of the chromosphere are here and
   there thrown up into enormous tongues of flame.

Source : WordNet®

chromosphere
     n : a gaseous layer of the sun's atmosphere (extending from the
         photosphere to the corona) that is visible during a total
         eclipse of the sun