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The Lorentz force in atmospheres of CP stars: theta Aurigae
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Astronomy and Space Physics.
2007 (English)In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 464, no 3, 1089-1099 p.Article in journal (Refereed) Published
##### Abstract [en]

Several dynamical processes may induce considerable electric currents in the atmospheres of magnetic chemically peculiar (CP) stars. The Lorentz force, which results from the interaction between the magnetic field and the induced currents, modifies the atmospheric structure and induces characteristic rotational variability of the hydrogen Balmer lines. To study this phenomena we have initiated a systematic spectroscopic survey of the Balmer lines variation in magnetic CP stars. In this paper we continue presentation of results of the program focusing on the high-resolution spectral observations of A0p star \aur (HD 40312). We have detected a significant variability of the H$\alpha$, H$\beta$, and H$\gamma$ spectral lines during full rotation cycle of the star. This variability is interpreted in the framework of the model atmosphere analysis, which accounts for the Lorentz force effects. Both the inward and outward directed Lorentz forces are considered under the assumption of the axisymmetric dipole or dipole+quadrupole magnetic field configurations. We demonstrate that only the model with the outward directed Lorentz force in the dipole+quadrupole configuration is able to reproduce the observed hydrogen line variation. These results present new strong evidences for the presence of non-zero global electric currents in the atmosphere of an early-type magnetic star.

##### Place, publisher, year, edition, pages
2007. Vol. 464, no 3, 1089-1099 p.
##### Keyword [en]
Stars; chemically peculiar Stars; magnetic fields Stars; atmospheres
##### National Category
Astronomy, Astrophysics and Cosmology
##### Identifiers
ISI: 000244756800042OAI: oai:DiVA.org:uu-14071DiVA: diva2:41841
Available from: 2008-01-28 Created: 2008-01-28 Last updated: 2011-02-10Bibliographically approved

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Kochukhov, Oleg
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Department of Astronomy and Space Physics
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Astronomy and Astrophysics
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Astronomy, Astrophysics and Cosmology