Bibcode
del Toro Iniesta, Jose Carlos; Ruiz Cobo, Basilio
Bibliographical reference
Living Reviews in Solar Physics, Volume 13, Issue 1, article id. 4, 84 pp.
Advertised on:
12
2016
Journal
Citations
61
Refereed citations
53
Description
Since the early 1970s, inversion techniques have become the most useful
tool for inferring the magnetic, dynamic, and thermodynamic properties
of the solar atmosphere. Inversions have been proposed in the literature
with a sequential increase in model complexity: astrophysical inferences
depend not only on measurements but also on the physics assumed to
prevail both on the formation of the spectral line Stokes profiles and
on their detection with the instrument. Such an intrinsic model
dependence makes it necessary to formulate specific means that include
the physics in a properly quantitative way. The core of this physics
lies in the radiative transfer equation (RTE), where the properties of
the atmosphere are assumed to be known while the unknowns are the four
Stokes profiles. The solution of the (differential) RTE is known as the
direct or forward problem. From an observational point of view, the
problem is rather the opposite: the data are made up of the observed
Stokes profiles and the unknowns are the solar physical quantities.
Inverting the RTE is therefore mandatory. Indeed, the formal solution of
this equation can be considered an integral equation. The solution of
such an integral equation is called the inverse problem. Inversion
techniques are automated codes aimed at solving the inverse problem. The
foundations of inversion techniques are critically revisited with an
emphasis on making explicit the many assumptions underlying each of
them.