A&A 433, 701-705 (2005)
Comparing magnetic field extrapolations with measurements of magnetic loopsT. Wiegelmann, A. Lagg, S. K. Solanki, B. Inhester and J. Woch
Max-Planck-Institut für Sonnensystemforschung, Max-Planck-Straße 2, 37191 Katlenburg-Lindau, Germany
(Received 6 September 2004 / Accepted 2 December 2004)
We compare magnetic field extrapolations from a photospheric magnetogram with the observationally inferred structure of magnetic loops in a newly developed active region. This is the first time that the reconstructed 3D-topology of the magnetic field is available to test the extrapolations. We compare the observations with potential fields, linear force-free fields and non-linear force-free fields. This comparison reveals that a potential field extrapolation is not suitable for a reconstruction of the magnetic field in this young, developing active region. The inclusion of field-line-parallel electric currents, the so called force-free approach, gives much better results. Furthermore, a non-linear force-free computation reproduces the observations better than the linear force-free approximation, although no free parameters are available in the former case.
Key words: Sun: magnetic fields -- Sun: corona -- Sun: chromosphere
© ESO 2005