THE MEAN-FIELD DYNAMO MODEL IN GEODYNAMO
Abstract and keywords
Abstract (English):
The 2D Parker's mean-field dynamo equations with a various distributions of the #x3B1;- and #x3C9;-effects are considered. We show that smooth profiles of #x3B1; and #x3C9; can produce dipole configuration of the magnetic field with the realistic magnetic energy spectrum. We emphasize that fluctuating #x3B1;-effect leads to increase of the magnetic energy at the small scales, breaking the dipole configuration of the field. The considered geostrophic profiles of #x3B1; and #x3C9; correspond to the small-scale polarwards/equatorwards travelling waves with the small dipole field contribution. The same result is observed for the dynamic form of the #x3B1;-quenching, where two branches of the weak and strong solution coexist.

Keywords:
Earth's liquid core, turbulence, geodynamo
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References

1. Belvedere, A two-dimensional asymptotic solution for a dynamo wave in the light of the solar internal rotation, // Mon. Not. R. Astron. Soc., v. 315, 2000.

2. Braginsky, Nearly axially symmetric model of the hydromagnetic dynamo of the Earth, I, Geomagn. Aeron., v. 15, 1975.

3. Brandenburg, Astrophysical magnetic fields and nonlinear dynamo theory, // Phys. Rep., v. 417, 2005., doi:https://doi.org/10.1016/j.physrep.2005.06.005

4. Christensen, Numerical modeling of the geodynamo: a systematic parameter study, // Geophys. J. Int., v. 138, 1999.

5. Finlay, International Geomagnetic Reference Field: the eleventh generation, // Geophys. J. Int., v. 183, no. 3, 2010., doi:https://doi.org/10.1111/j.1365-246X.2010.04804.x

6. Hejda, Nonlinearity in dynamo, // Geophys. Astrophys. Fluid Dynam., v. 104, no. 6, 1993., doi:https://doi.org/10.1080/03091929.2010.496365

7. Hoyng, Helicity fluctuations in mean field theory: an explanation for the variability of the solar cycle?, // Astron. Astrophys., v. 272, 1993.

8. Jones, Convection-driven geodynamo models, // Phil. Trans.~R.~Soc.~London, v. A358, 2000., doi:https://doi.org/10.1098/rsta.2000.0565

9. Jouve, A solar mean field dynamo benchmark, // Astron. Astrophys., v. 483, 2008., doi:https://doi.org/10.1051/0004-6361:20078351

10. Kleeorin, Magnitude of dynamo-generated magnetic field in solar-type convective zones, // Astronomy and Astrophysics, v. 297, 1995.

11. Kraichnan, Two-dimensional turbulence, Rep. Prog. Phys., v. 43, 1980.

12. Krause, Mean-Field Magnetohydrodynamics and Dynamo Theory, 1980.

13. Langel, The Main Field, Geomagnetism, edited by J. A. Jacobs, v. 1, 1987.

14. Moss, Polar branches of stellar activity waves: dynamo models and observations, // Astronomy and Astrophysics, v. 531, 2011., doi:https://doi.org/10.1051/0004-6361/201015949

15. Moss, Reversals of the solar dipole, // Astronomy and Astrophysics, v. 550, 2013., doi:https://doi.org/10.1051/0004-6361/201220766

16. Pedlosky, Geophysical Fluid Dynamics, 2nd ed., 1987.

17. Pouquet, Strong MHD helical turbulence and the nonlinear dynamo effect, // J. Fluid Mech., v. 77, 1976.

18. Reshetnyak, Geomagnetic field intensity and suppression of helicity in the geodynamo, // Izvestiya, Physics of the Solid Earth, v. 39, no. 9, 2003.

19. Reshetnyak, Taylor cylinder and convection in a spherical shell, // Geomagn. Aeron., v. 50, no. 2, 2010., doi:https://doi.org/10.1134/S0016793210020143

20. Reshetnyak, Geostrophic balance and reversals of the geomagnetic field, // Russ. J. Earth Sci., v. 13, 2013., doi:https://doi.org/10.2205/2013ES000526

21. Roberts, On the genesis of the Earth's magnetism, // Rep. Prog. Phys., v. 76, no. 9, 2013., doi:https://doi.org/10.1088/0034-4885/76/9/096801

22. Sobko, Geomagnetic reversals in a simple geodynamo model, // Geomagnetism and Aeronomy, v. 52, no. 2, 2012., doi:https://doi.org/10.1134/S0016793212020144

23. Wicht, Inner-core conductivity in numerical dynamo simulations, // Phys. Earth Planet. Int., v. 132, 2002., doi:https://doi.org/10.1016/S0031-92010200078-X

24. Zeldovich, Magnetic Fields in Astrophysics, 1990.

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