EAS Publications Series
Volume 18, 2006Radiative Transfer and Applications to Very Large Telescopes
|Page(s)||1 - 23|
|Published online||08 March 2006|
Ph. Stee (ed)
EAS Publications Series, 18 (2006) 1-23
Why is it so difficult to solve the radiative transfer equation?
Centre de Recherche Astrophysique de Lyon (UMR 5574 du CNRS), Observatoire de Lyon, 9 avenue Charles André,
69561 Saint-Genis-Laval Cedex, France
2 Observatoire de Paris-Meudon, Laboratoire LUTH, 5 place Jules Janssen, 92195 Meudon Cedex, France
The equation of transfer is a two-faced equation, easy to solve at times, and difficult to solve at other times, depending on the values assumed by its coefficients. It is rather tractable when applied to the deep layers of atmospheres and for frequencies from their continuum spectrum, but this solvability is in stark contrast to the difficulty in solving it close to the surface of atmospheres or within spectral lines. It follows that the photons most rich in information that reach our telescopes are also the most difficult to interpret. The purpose of this note is to stress this point and to illustrate it with some examples taken from the solar atmosphere.
© EAS, EDP Sciences, 2006