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Magnetic Fields: Observations and Topology

Published online by Cambridge University Press:  12 April 2016

J. D. Landstreet
J. D. Landstreet*
Affiliation:
Department of Astronomy, University of Western Ontario, LondonOntarioCanadaN6A 3K7, and Observatoire Midi-Pyrénées, 14 ave. Edouard Belin, 31400 Toulouse, France

Abstract

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To understand the complex physical processes revealed by the wide variety of surface chemical abundances and the inhomogeneous distributions of various elements over the surfaces of magnetic Ap and Bp stars, it is important to be able to describe the surface magnetic field structure. For most magnetic stars, the available observations are far from sufficient to define the surface magnetic structure even with low resolution, but more extensive and constraining observations are gradually becoming available for a small set of stars. This paper discusses the extent to which the surface field structure can be defined for stars for which only the usual measurements (essentially the variation of the mean longitudinal field strength Bɩ with rotational phase) are available, and how further information (variation of mean field modulus Bs with phase, line profile observations, and circular and linear spectropolarimetry of absorption lines or broad-band radiation) can be used to obtain a much more detailed picture of the magnetic field structure.

Type
II. Magnetic Fields: Observations and Theories
Information
International Astronomical Union Colloquium , Volume 138: Peculiar versus Normal Phenomena in A-Type and Related Stars , 1993 , pp. 218 - 231
Copyright
Copyright © Astronomical Society of the Pacific 1993

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