The chromosphere (coming from from chromos, the Greek word for colour) is an 2500 km thick layer of gas that lies above the Suns photosphere and under the heliosphere.

Within this layer the temperature rises from 6000K to about 20000K causing the hydrogen that makes up the vast proportion of this layer emit a reddish coloured light (caused by H-alpha emissions). In the visual spectrum, these emissons can be seen in prominences that project above the disc of the sun during total solar eclipses. However, when the Sun is viewed through a filter that isolates the H-alpha wavelengths, many new details show up within the chromosphere that would otherwise be missed, including bright rings around sunspots (known as plage), the chromospheric network of magnetic fields, and dark filaments across the disc itself

The chromosphere is also home to spikes of gas called spicules that rise through it at the edges of the large convection cells that exist within the layer (so called supergranules). These are short-lived phenomena, corresponding to rising jets of gas that move upward at about 30km/sec and last only about 10 minutes. Other phenomena that can be observed include solar flares, prominence and filament eruptions.

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