Abstract
The first consistent model for the turbulent tachocline is presented, with the turbulent diffusivity computed within the model instead of being specified arbitrarily. For the origin of the 3D turbulence a new mechanism is proposed. Owing to the strongly stable stratification, the mean radial shear is stable, while the horizontal shear is expected to drive predominantly horizontal, quasi-2D motions in thin slabs. Here I suggest that a major source of 3D overturning turbulent motions in the tachocline is the secondary shear instability due to the strong, random vertical shear arising between the uncorrelated horizontal flows in neighboring slabs. A formula for the vertical diffusivity due to this turbulence, Equation (9), is derived and applied in a simplified 1D model of the tachocline. It is found that Maxwell stresses due to an oscillatory poloidal magnetic field of a few hundred gauss are able to confine the tachocline to a thickness less than 5 Mm. The integral scale of the 3D overturning turbulence is the buoyancy scale, on the order of 10 km, and its velocity amplitude is a few m s−1, yielding a vertical turbulent diffusivity on the order of 108 cm2 s−1.
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References
Basu, S. and Antia, H. M.: 2001, Monthly Notices Royal Astron. Soc. 324, 498.
Cally, P. S.: 2001, Solar Phys. 199, 231.
Charbonneau, P., Dikpati, M., and Gilman, P. A.: 1999, Astrophys. J. 526, 523.
Dikpati, M. and Gilman, P. A.: 2001, Astrophys. J. 551, 536.
Dziembowski, W. and Kosovichev, A.: 1987, Acta Astr. 37, 341.
Forgács-Dajka, E.: 2003, Astron. Astrophys., submitted.
Forgács-Dajka, E. and Petrovay, K.: 2001, Solar Phys. 203, 195.
Forgács-Dajka, E. and Petrovay, K.: 2002, Astron. Astrophys. 389, 629.
Garaud, P.: 2001a, Monthly Notices Royal Astron. Soc. 329, 1.
Garaud, P.: 2001b, Monthly Notices Royal Astron. Soc. 324, 68.
Gilman, P. A. and Dikpati, M.: 2000, Astrophys. J. 528, 552.
Gough, D. O. and McIntyre, M. E.: 1998, Nature 394, 755.
Hopfinger, E. J.: 1987, J. Geophys. Res. 92, 5287.
Jacobitz, F. G. and Sarkar, S.: 1998, Phys. Fluids 10, 1158.
Kaltenbach, H.-J., Gerz, T., and Schumann, U.: 1994, J. Fluid Mech. 280, 1.
Kosovichev, A. G.: 1996, Astrophys. J. 469, L61.
MacGregor, K. B. and Charbonneau, P.: 1999, Astrophys. J. 519, 911.
Marik, D. and Petrovay, K.: 2003, Astron. Astrophys. 396, 1011.
Métais, O. and Herring, J. R.: 1989, J. Fluid Mech. 202, 117.
Miesch, M. S.: 2001, Astrophys. J. 562, 1058.
Miesch, M. S.: 2002, Astrophys. J., in press.
Petrovay, K.: 2000, in The Solar Cycle and Terrestrial Climate, ESA Publ. SP-463, p. 3.
Petrovay, K. and Szakály, G.: 1999, Solar Phys. 185, 1.
Rüdiger, G. and Kitchatinov, L. L.: 1997, Astr. Nachr. 318, 273.
Speziale, C. G.: 1991, Ann. Rev. Fluid Mech. 23, 107.
Spiegel, E. A. and Zahn, J.-P.: 1992, Astron. Astrophys. 265, 106.
Spruit, H. C.: 1999, Astron. Astrophys. 349, 189.
Tassoul, J.-L.: 1978, Theory of Rotating Stars, Princeton University Press, New York.
Thorpe, S. A.: 1987, J. Geophys. Res. 92, 5231.
Werne, J. and Fritts, D. C.: 1999, Geophys. Res. Lett. 26, 439.
Xiong, D. R. and Deng, L.: 2001, Monthly Notices Royal Astron. Soc. 327, 1137.
Zahn, J.-P.: 1983, in A. N. Cox et al. (ed.), Astrophysical Processes in Upper Main Sequence Stars, Proc. Saas-Fee Winter School, Geneva Obs., p. 225.
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Petrovay, K. A Consistent one-Dimensional Model for the Turbulent Tachocline. Solar Physics 215, 17–30 (2003). https://doi.org/10.1023/A:1024880723754
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DOI: https://doi.org/10.1023/A:1024880723754