Bibcode
Müller, D. A. N.; Schlichenmaier, R.; Fritz, G.; Beck, C.
Bibliographical reference
Astronomy and Astrophysics, Volume 460, Issue 3, December IV 2006, pp.925-933
Advertised on:
12
2006
Journal
Citations
19
Refereed citations
14
Description
Context: .Sunspot penumbrae harbor highly structured magnetic fields and
flows. The moving flux tube model offers an explanation for several
observed phenomena, e.g. the Evershed effect and bright penumbral
grains. Aims: .A wealth of information can be extracted from
spectropolarimetric observations. In order to deduce the structure of
the magnetic field in sunspot penumbrae, detailed forward modeling is
necessary. On the one hand, it gives insight into the sensitivity of
various spectral lines to different physical scenarios. On the other
hand, it is a very useful tool to guide inversion techniques. In this
work, we present a generalized 3D geometrical model that embeds an
arbitrarily shaped flux tube in a stratified magnetized atmosphere. Methods: .The new semi-analytical geometric model serves as a
frontend for a polarized radiative transfer code. The advantage of this
model is that it preserves the discontinuities of the physical
parameters across the flux tube boundaries. This is important for the
detailed shape of the emerging Stokes Profiles and the resulting net
circular polarization (NCP). Results: .(a) The inclination of
downflows in the outer penumbra must be shallower than approximately
15° (b) observing the limb-side NCP of sunspots in the Fe I 1564.8
nm line offers a promising way to identify a reduced magnetic field
strength in flow channels; (c) the choice of the background atmosphere
can significantly influence the shape of the Stokes profiles, but does
not change the global characteristics of the resulting NCP curves for
the tested atmospheric models.