Editing Stellar corona (section)

===Radiation===
{{see also|Coronal radiative losses}}
Coronal plasma is optically thin and therefore transparent to the [[electromagnetic radiation]] that it emits and to that coming from lower layers. The plasma is very rarefied and the [[photon]] [[mean free path]] overcomes by far all the other length-scales, including the typical sizes of common coronal features.{{citation needed|date=January 2022}}

Electromagnetic radiation from the corona has been identified coming from three main sources, located in the same volume of space: 
* The K-corona (K&nbsp;for {{lang|de|kontinuierlich}}, "continuous" in German) is created by sunlight [[Thomson scattering]] off free [[electron]]s; [[doppler broadening]] of the reflected photospheric [[absorption line]]s spreads them so greatly as to completely obscure them, giving the spectral appearance of a continuum with no absorption lines. 
* The F-corona (F&nbsp;for [[Joseph von Fraunhofer|Fraunhofer]]) is created by sunlight bouncing off dust particles, and is observable because its light contains the Fraunhofer absorption lines that are seen in raw sunlight; the F-corona extends to very high [[elongation (astronomy)|elongation]] angles from the Sun, where it is called the [[zodiacal light]]. 
* The E-corona (E for emission) is due to spectral emission lines produced by ions that are present in the coronal plasma; it may be observed in broad or [[forbidden line|forbidden]] or hot [[spectral line|spectral emission lines]] and is the main source of information about the corona's composition.<ref name="Corfield">{{cite book
|last=Corfield
|first=Richard
|year=2007
|title=Lives of the Planets
|publisher=Basic Books
|isbn=978-0-465-01403-3
|url-access=registration
|url=https://archive.org/details/livesofplanetsna00corf
}}
</ref>