A plage is a bright region in the chromosphere of the Sun, 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, 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.
- Encyclopedia of Astrobiology, Astronomy & Spaceflight: Plage