The description of the word you requested from the astronomical dictionary is given below.
chrooma = [Greek] color; sphairos = [Greek] ball
The chromosphere is a layer in the Sun that is roughly between about 250 miles (400 km) and 1300 miles (2100 km) above the solar surface. The temperature in the chromosphere varies between about 4000 K at the bottom (the so-called temperature minimum) and 8000 K at the top (6700 and 14,000 degrees F, 3700 and 7700 degrees C), so in this layer (and higher layers) it actually gets hotter if you go further away from the Sun. The density in the chromosphere is much, much smaller than the density of air at sea level on Earth. At the top of the chromosphere there are only about 10 thousand million atoms in each cubic centimetre (100 thousand million atoms per cubic inch). The chromosphere shows up in images taken in the center of the H-alpha spectral line and also (briefly) near the beginning and end of a total solar eclipse.