Astronomy and Astrophysics – Astrophysics – Solar and Stellar Astrophysics
Scientific paper
2009-03-05
Astronomy and Astrophysics
Astrophysics
Solar and Stellar Astrophysics
Proceedings of IAU Symposium 259, Cosmic Magnetic Fields: from Planets, to Stars and Galaxies Ed.: K. G. Strassmeier, A. G. Ko
Scientific paper
10.1017/S1743921309031469
Zeeman-Doppler Imaging (ZDI) is a powerful inversion method to reconstruct stellar magnetic surface fields. The reconstruction process is usually solved by translating the inverse problem into a regularized least-square or optimization problem. In this contribution we will emphasize that ZDI is an inherent non-linear problem and the corresponding regularized optimization is, like many non-linear problems, potentially prone to local minima. We show how this problem will be exacerbated by using an inadequate forward model. To facilitate a more consistent full radiative transfer driven approach to ZDI we describe a two-stage strategy that consist of a principal component analysis (PCA) based line profile reconstruction and a fast approximate polarized radiative transfer method to synthesize local Stokes profiles. Moreover, we introduce a novel statistical inversion method based on artificial neural networks (ANN) which provide a fast calculation of a first guess model and allows to incorporate better physical constraints into the inversion process.
Carroll Andrew T.
Ilyin I. I.
Kopf Markus
Strassmeier Klaus G.
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