Plage (astronomy)
Encyclopedia
A plage is a bright region in the chromosphere
Chromosphere
The chromosphere is a thin layer of the Sun's atmosphere just above the photosphere, roughly 2,000 kilometers deep....

 of the Sun
Sun
The Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields...

, typically found in regions of the chromosphere near sunspots.
The term itself is poetically taken from the French word for "beach." The plage regions map closely to the faculae in the photosphere below, but the latter have much smaller spatial scales. Accordingly plage occurs most visibly near a sunspot region. Faculae have a strong influence on the
solar constant
Solar constant
The solar constant, a measure of flux density, is the amount of incoming solar electromagnetic radiation per unit area that would be incident on a plane perpendicular to the rays, at a distance of one astronomical unit...

, and the more readily detectable (because chromospheric) plage areas traditionally are used to monitor this influence. In this context "active network" consists of plage-like brightenings extending away from active regions as their magnetism appears to diffuse into the quiet Sun, but constrained to follow the network boundaries.

Because we can explain faculae with the strictly photospheric "hot wall" model, it is not clear what the
actual physical relationship between plage and faculae may be.

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