Dependence of the properties of magnetic fluxtubes on area factor or amount of flux |
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| Authors: | J O Stenflo J W Harvey |
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| Institution: | (1) Institute of Astronomy, ETH-Zentrum, CH-S092 Zürich, Switzerland;(2) National Solar Observatory, P.O. Box 26732, 85726 Tucson, AZ, USA |
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| Abstract: | Stokes I and V line profiles with high signal-to-noise ratio of the 1 Fei  5247.06 and 5250.22 Å lines have been recorded in a number of regions with different amount of magnetic flux near disc center, from  non-magnetic regions to strong plages. The objective has been to study how the intrinsic fluxtube properties may depend on the amount of flux concentration, i.e., on the magnetic area factor. Indirectly, the area factor should be related to the average fluxtube diameter.The intrinsic kG field strength is found to vary only slowly, by at most a few hundred G, when the area factor increases by a factor of 6. The statistical spread in the values is quite small.The wavelength positions of the V profiles do not indicate any downdrafts within the fluxtubes. The well-known association of redward line shifts and magnetic features probably arises from motions in the field-free region adjacent to the fluxtubes. There are strong asymmetries of the Stokes V profile always in the sense of a 20–30% stronger blue peak, which indicate that there must be important mass motions with a vertical gradient within the fluxtubes.Most of the recordings have been made with a grating spectrometer, but two recordings with a Fourier transform spectrometer have provided an important check of the instrumental effects of limited spectral resolution and straylight in the spectrometer data. These effects modify the I and V profiles substantially, and can for instance result in fictitious redshifts derived from the Stokes V profiles.Operated by the Association of Universities for Research in Astronomy, Inc., under contract with the National Science Foundation. |
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