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Magnetic mixing in red giant and asymptotic giant branch stars

Nordhaus, J. and Busso, M. and Wasserburg, G. J. and Blackman, E. G. and Palmerini, S. (2008) Magnetic mixing in red giant and asymptotic giant branch stars. Astrophysical Journal Letters, 684 (1). L29-L32. ISSN 2041-8205. doi:10.1086/591963.

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The available information on isotopic abundances in the atmospheres of low-mass red giant branch (RGB) and asymptotic giant branch (AGB) stars requires that episodes of extensive mixing occur below the convective envelope, reaching down to layers close to the hydrogen burning shell (cool bottom processing). Recently, it was suggested that dynamo-produced buoyant magnetic flux tubes could provide the necessary physical mechanisms and also supply sufficient transport rates. Here, we present an α-Ω dynamo in the envelope of an RGB/AGB star in which shear and rotation drain via turbulent dissipation and Poynting flux. In this context, if the dynamo is to be sustained throughout either phase, convection must resupply shear. Under this condition, volume-averaged peak toroidal field strengths of <B_Ø> ≃ 3 × 10^3 G (RGB) and <B_Ø> ≃ 5 × 10^3 G (AGB) are possible at the base of the convection zone. If the magnetic fields are concentrated in flux tubes, the corresponding field strengths are comparable to those required by cool bottom processing.

Item Type:Article
Related URLs:
URLURL TypeDescription
Wasserburg, G. J.0000-0002-7957-8029
Additional Information:© 2008 The American Astronomical Society. Received 2008 June 24; accepted 2008 July 17; published 2008 August 20. J. N. and E. G. B. acknowledge support from SST grant GO-50134 and NSF grant AST-0406799. M. B. acknowledges support from MURST (PRIN2006-022731). G. J. W. acknowledges the support of DOE-FG03-88ER13851 and the generosity of the Epsilon Foundation and the California Institute of Technology’s contribution 9178(1123).
Funding AgencyGrant Number
Spitzer Space Telescope (SST)GO-50134
Ministero per l'Università e per la Ricerca Scientifica e Tecnologica (MURST)PRIN2006-022731
Department of EnergyFG03-88ER13851
Epsilon FoundationUNSPECIFIED
Subject Keywords:MHD; stars: abundances; stars: AGB and post-AGB; stars: interiors; stars: magnetic fields; stars: rotation
Other Numbering System:
Other Numbering System NameOther Numbering System ID
Caltech Division of Geological and Planetary Sciences9178
Lunatic Asylum Lab1123
Issue or Number:1
Record Number:CaltechAUTHORS:20090518-075933248
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Official Citation:Magnetic Mixing in Red Giant and Asymptotic Giant Branch Stars J. Nordhaus, M. Busso, G. J. Wasserburg, E. G. Blackman, and S. Palmerini 2008 ApJ 684 L29-L32 doi: 10.1086/591963
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:14248
Deposited By: Tony Diaz
Deposited On:18 Aug 2009 20:45
Last Modified:08 Nov 2021 22:44

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