MAGNETO-THERMOHALINE MIXING IN RED GIANTS

Denissenkov, Pavel A; Pinsonneault, Marc

doi:10.1088/0004-637X/696/2/1823; COUNTRY OF INPUT: INTERNATIONAL ATOMIC ENERGY AGENCY (IAEA)

Title: MAGNETO-THERMOHALINE MIXING IN RED GIANTS

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Abstract

We revise a magnetic buoyancy model that has recently been proposed as a mechanism for extra mixing in the radiative zones of low-mass red giants. The most important revision is our accounting of the heat exchange between rising magnetic flux rings and their surrounding medium. This increases the buoyant rising time by five orders of magnitude; therefore, the number of magnetic flux rings participating in the mixing has to be increased correspondingly. On the other hand, our revised model takes advantage of the fact that the mean molecular weight of the rings formed in the vicinity of the hydrogen burning shell has been reduced by {sup 3}He burning. This increases their thermohaline buoyancy (hence, decreases the total ring number) considerably, making it equivalent to the pure magnetic buoyancy produced by a frozen-in toroidal field with B {sub {psi}} {approx} 10 MG. We emphasize that some toroidal field is still needed for the rings to remain cohesive while rising. Besides, this field prevents the horizontal turbulent diffusion from eroding the {mu} contrast between the rings and their surrounding medium. We propose that the necessary toroidal magnetic field is generated by differential rotation of the radiative zone that stretches a preexisting poloidalmore »« less

Authors:

Denissenkov, Pavel A; Pinsonneault, Marc ^[1]

Department of Astronomy, Ohio State University, 4055 McPherson Laboratory, 140 West 18th Avenue, Columbus, OH 43210 (United States)

Publication Date:: Sun May 10 00:00:00 EDT 2009

OSTI Identifier:: 21300661

Resource Type:: Journal Article

Journal Name:: Astrophysical Journal

Additional Journal Information:: Journal Volume: 696; Journal Issue: 2; Other Information: DOI: 10.1088/0004-637X/696/2/1823; Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0004-637X

Country of Publication:: United States

Language:: English

Subject:: 79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; 99 GENERAL AND MISCELLANEOUS//MATHEMATICS, COMPUTING, AND INFORMATION SCIENCE; ABUNDANCE; HELIUM 3; HYDROGEN BURNING; MAGNETIC FIELDS; MAGNETIC FLUX; ROTATION; STAR EVOLUTION; STARS

Citation Formats


                    Denissenkov, Pavel A, Pinsonneault, Marc, and MacGregor, Keith B. MAGNETO-THERMOHALINE MIXING IN RED GIANTS.  United States: N. p., 2009. 
        Web.  doi:10.1088/0004-637X/696/2/1823; COUNTRY OF INPUT: INTERNATIONAL ATOMIC ENERGY AGENCY (IAEA).

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                    Denissenkov, Pavel A, Pinsonneault, Marc, & MacGregor, Keith B. MAGNETO-THERMOHALINE MIXING IN RED GIANTS.  United States.  https://doi.org/10.1088/0004-637X/696/2/1823; COUNTRY OF INPUT: INTERNATIONAL ATOMIC ENERGY AGENCY (IAEA)

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                    Denissenkov, Pavel A, Pinsonneault, Marc, and MacGregor, Keith B. 2009.  
        "MAGNETO-THERMOHALINE MIXING IN RED GIANTS".  United States.  https://doi.org/10.1088/0004-637X/696/2/1823; COUNTRY OF INPUT: INTERNATIONAL ATOMIC ENERGY AGENCY (IAEA).

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@article{osti_21300661,

  title        = {MAGNETO-THERMOHALINE MIXING IN RED GIANTS},

  author       = {Denissenkov, Pavel A and Pinsonneault, Marc and MacGregor, Keith B.},

  abstractNote = {We revise a magnetic buoyancy model that has recently been proposed as a mechanism for extra mixing in the radiative zones of low-mass red giants. The most important revision is our accounting of the heat exchange between rising magnetic flux rings and their surrounding medium. This increases the buoyant rising time by five orders of magnitude; therefore, the number of magnetic flux rings participating in the mixing has to be increased correspondingly. On the other hand, our revised model takes advantage of the fact that the mean molecular weight of the rings formed in the vicinity of the hydrogen burning shell has been reduced by {sup 3}He burning. This increases their thermohaline buoyancy (hence, decreases the total ring number) considerably, making it equivalent to the pure magnetic buoyancy produced by a frozen-in toroidal field with B {sub {psi}} {approx} 10 MG. We emphasize that some toroidal field is still needed for the rings to remain cohesive while rising. Besides, this field prevents the horizontal turbulent diffusion from eroding the {mu} contrast between the rings and their surrounding medium. We propose that the necessary toroidal magnetic field is generated by differential rotation of the radiative zone that stretches a preexisting poloidal field around the rotation axis, and that magnetic flux rings are formed as a result of its buoyancy-related instability.},

  doi          = {10.1088/0004-637X/696/2/1823; COUNTRY OF INPUT: INTERNATIONAL ATOMIC ENERGY AGENCY (IAEA)},

  url          = {https://www.osti.gov/biblio/21300661},
  journal      = {Astrophysical Journal},

  issn         = {0004-637X},

  number       = 2,

  volume       = 696,

  place        = {United States},

  year         = {Sun May 10 00:00:00 EDT 2009},

  month        = {Sun May 10 00:00:00 EDT 2009}

}

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https://doi.org/10.1088/0004-637X/696/2/1823; COUNTRY OF INPUT: INTERNATIONAL ATOMIC ENERGY AGENCY (IAEA)

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