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Cross Helicity and Turbulent Magnetic Diffusivity in the Solar Convection Zone
Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Nordic Institute for Theoretical Physics (Nordita).
2011 (English)In: Solar Physics, ISSN 0038-0938, E-ISSN 1573-093X, Vol. 269, no 1, 3-12 p.Article in journal (Refereed) Published
Abstract [en]

In a density-stratified turbulent medium, the cross helicity (u' . B') is considered as a result of the interaction of the velocity fluctuations and a large-scale magnetic field. By means of a quasilinear theory and by numerical simulations, we find the cross helicity and the mean vertical magnetic field to be anti-correlated. In the high-conductivity limit the ratio of the helicity and the mean magnetic field equals the ratio of the magnetic eddy diffusivity and the (known) density scale height. The result can be used to predict that the cross helicity at the solar surface will exceed the value of 1 gauss km s(-1). Its sign is anti-correlated to that of the radial mean magnetic field. Alternatively, we can use our result to determine the value of the turbulent magnetic diffusivity from observations of the cross helicity.

Place, publisher, year, edition, pages
2011. Vol. 269, no 1, 3-12 p.
Keyword [en]
Magnetohydrodynamics (MHD), Sun: magnetic field
National Category
Astronomy, Astrophysics and Cosmology
URN: urn:nbn:se:su:diva-69443DOI: 10.1007/s11207-010-9683-4ISI: 000288626700001OAI: diva2:478194
authorCount :3Available from: 2012-01-16 Created: 2012-01-12 Last updated: 2012-01-16Bibliographically approved

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Brandenburg, Axel
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Department of AstronomyNordic Institute for Theoretical Physics (Nordita)
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