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Astron. Astrophys. 364, L101-L104 (2000)

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Letter to the Editor

Successful spectral synthesis of Zeeman-split molecular bands in sunspot spectra

S.V. Berdyugina 1, C. Frutiger 2, S.K. Solanki 3 and W. Livingstone 4

1 University of Oulu, Astronomy Division, P.O. Box 3000, 90014 Finland
2 ETHZ, Institut für Astronomie, Scheuchzerstrasse 7, 8092 Zürich, Switzerland
3 Max-Planck-Institut für Aeronomie, Max-Planck-Strasse 2, 37191 Katlenburg-Lindau, Germany
4 National Solar Observatory, AURA, P.O. Box 26732, Tucson, AZ 85726, USA

Received 26 October 2000 / Accepted 20 November 2000


We present the first spectral synthesis of Zeeman-split Stokes profiles of the MgH [FORMULA]-[FORMULA] green system and TiO [FORMULA]-system. The calculations involve different regimes of the molecular Zeeman effect, up to the complete Paschen-Back effect for individual lines. The synthetic spectra are compared with observations of Stokes I and V in sunspot umbrae. We find that although the Stokes I spectra are reasonably reproduced, some lines are obviously still missing from the employed line lists. The Stokes V spectra turn out to be much cleaner since the missing lines do not appear to be Zeeman-split. We thus provide the first good fit to Zeeman-split molecular lines, including profiles with unconventional Stokes V shapes, determined by the Paschen-Back effect.

Key words: Sun: magnetic fields – Sun: sunspots – line: formation – polarization – molecular processes

Send offprint requests to: S.V.Berdyugina (sveta@ukko.oulu.fi)

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© European Southern Observatory (ESO) 2000

Online publication: January 29, 2001