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Average Variations of Photospheric FeI and FeII Line Parameters as Function of the Magnetic Filling Factor

Published online by Cambridge University Press:  08 February 2017

P.N. Brandt  and
M. Steinegger
P.N. Brandt
Affiliation:
1Kiepenheuer-Institut für Sonnenphysik Schöneckstr. 6 D-7800 FREIBURG, F.R.G.
M. Steinegger
Affiliation:
2Insitut für Astronomie Universitåtsplatz 5 A-8010 GRAZ, Austria

Abstract

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A series of 17 Fourier transform spectra taken at the McMath telescope near disk center in regions of different magnetic field strengths were analyzed. Applying a multi-variate regression analysis magnetic filling factors 0 < α ≥ 0.11 were determined. With α increasing from 0 to 0.11, line bisectors averaged over groups of lines of similar depth are found to show a blue shift decreasing from 0.35 km s–1 to nearly 0.1 km s–1, when referred to the MgI line λ5172.7å. The bisectors of FeII lines exhibit smaller blue shifts than FeI lines. The increase of bisector red shift near the continuum with increasing α, found earlier by Brandt and Solanki (1987), was confirmed and is tentatively interpreted as a manifestation of downdrafts in the vicinity of flux tubes (Deinzer et al., 1984).

A significant increase of line width (typically between 3 and 8%, depending on line strength) and a decrease of line depth is found with increasing filling factor. For strong lines the equivalent width W shows no variation or a slight increase, while for the weaker lines a reduction of W between a few % and > 10% is found.

Type
I. Global Properties of the Photosphere
Information
Symposium - International Astronomical Union , Volume 138: Solar Photosphere: Structure, Convection and Magnetic Fields , 1990 , pp. 41 - 46
Copyright
Copyright © Kluwer 1990 

References

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