  This paper introduces a novel feature extraction technique for the analysis
of spectral line Stokes profiles. The procedure is based on the use of an
auto-associative artificial neural network containing non-linear hidden layers.
The neural network extracts a small subset of parameters from the profiles
(features), from which it is then able to reconstruct the original profile.
This new approach is compared to two other procedures that have been proposed
in previous works, namely principal component analysis and Hermitian function
expansions. Depending on the target application, each one of these three
techniques has some advantages and disadvantages, which are discussed here.

Astrophysics