The flash
spectrum of the Sun is the spectrum emitted by the outer layer of the sun known as the
chromosphere. It is usually
obscured by the light from the rest of the Sun, but can be observed during the few seconds of totality of a solar eclipse. A reddish glow is then seen coming from a thin region--the
chromosphere--around the solar limb. The red hue is produced by the strong emission of the hydrogen atom at a wavelength of 6,563 angstroms.Flash
spectrum analysis shows that the chromosphere is a layer of rapidly moving gases, at a temperature of about 8,000 K and a density around 10¦x7) gm/cm7. It extends to a height of about 7,000 km (4,350 mi) above the photosphere of the Sun.