Magnetic mixing in red giant and asymptotic giant branch stars
Abstract
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 ≃ 3 × 10^3 G (RGB) and ≃ 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.
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).Attached Files
Published - NORapjl08.pdf
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Additional details
- Eprint ID
- 14248
- Resolver ID
- CaltechAUTHORS:20090518-075933248
- Spitzer Space Telescope (SST)
- GO-50134
- NSF
- AST-0406799
- Ministero per l'Università e per la Ricerca Scientifica e Tecnologica (MURST)
- PRIN2006-022731
- Department of Energy
- FG03-88ER13851
- Epsilon Foundation
- Caltech
- 9178(1123)
- Created
-
2009-08-18Created from EPrint's datestamp field
- Updated
-
2021-11-08Created from EPrint's last_modified field
- Other Numbering System Name
- Lunatic Asylum Lab
- Other Numbering System Identifier
- 1123