A plage is a bright region in the

Sun The Sun is the star at the centre of the Solar System. It is a massive, nearly perfect sphere of hot plasma, heated to incandescence by nuclear fusion reactions in its core, radiating the energy from its surface mainly as visible light a ...

chromosphere A chromosphere ("sphere of color", from the Ancient Greek words χρῶμα (''khrôma'') 'color' and σφαῖρα (''sphaîra'') 'sphere') is the second layer of a Stellar atmosphere, star's atmosphere, located above the photosphere and below t ...

, typically found in and around

active regions In solar physics and observation, an active region is a temporary feature in the Sun's atmosphere characterized by a strong and complex magnetic field. They are often associated with sunspots and are commonly the source of violent eruptions such a ...

. Historically, they have been referred to as ''bright flocculi'', in contrast to dark flocculi, and as ''chromospheric faculae'', in contrast to photospheric faculae.

Etymology

The term is often believed to be poetically taken from the French word for "beach"; however, this is likely a misunderstanding of an 1893 article by

Henri-Alexandre Deslandres Henri Alexandre Deslandres (; 24 July 1853 – 15 January 1948) was a French astronomer, director of the Meudon and Paris Observatories, who carried out intensive studies on the behaviour of the atmosphere of the Sun. Biography Deslandres' u ...

where the name ''facular flames'' was suggested. In the article, Deslandres also refers to them as ''plages brillantes'', meaning ''bright regions'', which became the more commonly used term.

Description

Classically, plage have been defined as regions that are bright in Hα and other chromospheric

emission line A spectral line is a weaker or stronger region in an otherwise uniform and continuous spectrum. It may result from emission or absorption of light in a narrow frequency range, compared with the nearby frequencies. Spectral lines are often used ...

s. With modern imaging, most researchers now identify plage based on the

photospheric The photosphere is a star's outer shell from which light is radiated. It extends into a star's surface until the plasma becomes opaque, equivalent to an optical depth of approximately , or equivalently, a depth from which 50% of light will esca ...

magnetic field concentration of the

faculae Facula ( faculae) is a bright spot on the surface of a planet or a star. It may refer to * Solar facula * * Bright spots on Ceres * * * * {{disambig ...

below. The magnetic field of plage is confined to the intergranular lanes in the photosphere with a strength of around 1500 G, but expands into a volume filling canopy in the chromosphere with a field of around 450G. It is believed that plage is formed from decaying emerging flux regions, and often acts as a footprint for coronal loops and fibrils, which makes them an important interface for

coronal heating In astronomy, a corona (: coronas or coronae) is the outermost layer of a star's atmosphere. It is a hot but relatively dim region of plasma populated by intermittent coronal structures such as prominences, coronal loops, and helmet streamers. ...

References

External links

Encyclopedia of Astrobiology, Astronomy & Spaceflight: Plage
Stellar phenomena Solar phenomena {{sun-stub

Etymology

Description

See also

References

External links