Abstract
The continual emergence of magnetic flux in solar active regions suggests that a substantial reservoir of flux is present somewhere beneath the photosphere. It has been proposed that this flux could be stored in an azimuthal field of order 3000 G residing in the lower portion of the convection zone. Such a field may be large enough to substantially influence the dynamics of the convection: linear stability analyses indicate that donut-like convective rolls having azimuthal symmetry might then be preferred to banana cells aligned with the rotation axis. Observational detections of such azimuthal rolls have been claimed.
The problem of pattern selection by convection in the presence of rotation and a horizontal magnetic field is examined here in a model system consisting of a planar Boussinesq fluid layer. Nonlinear solutions are obtained numerically. It is found that solutions consisting solely of donut cells can exist even at parameter values at which linear theory suggests that banana cells should be preferred instead. However, when the horizontal field decays below a critical value, banana cells may then grow. This leads to the destruction of the horizontal field and a permanent transition to banana cells.
Similar content being viewed by others
References
Dogiel, V. A.: 1980, Solar Phys. 82, 427.
Eltayeb, I. A.: 1972, Proc. Roy. Soc. A326, 299.
Eltayeb, I. A. and Kumar, S.: 1977, Proc. Roy. Soc. A353, 145.
Gazdag, J.: 1976, J. Comp. Phys. 20, 196.
Gilman, P. A. and Miller, J.: 1986, Astrophys. J. Suppl. 61, 585.
Glatzmaier, G. A.: 1984, J. Comp. Phys. 55, 461.
Hughes, D. W.: 1985a, Geophys. Astrophys. Fluid Dyn. 32, 273.
Hughes, D. W.: 1985b, Geophys. Astrophys. Fluid Dyn. 34, 99.
Hurlburt, N. E. and Toomre, J.: 1988, Astrophys. J. 327, 920.
Jones, C. A. and Galloway, D. J.: 1988, in F. R. Stephenson and A. W. Wolfendale (eds.), Secular Solar and Geomagnetic Variations in the Last 10000 Years, Kluwer, Boston, p. 97.
Jones, C. A., Roberts, P. H., and Galloway, D. J.: 1989, Geophys. Astrophys. Fluid Dyn. (submitted).
Moffatt, H. K.: 1978, Magnetic Field Generation in Electrically Conducting Fluids, Cambridge University Press, Cambridge.
Orszag, S. A.: 1983, in M. Ghil, R. Benzi, and G. Parisi (eds.), Proceedings of the International School of Physics ‘Enrico Fermi’, Course LXXXVIII: Turbulence and Predictability in Geophysical Fluid Dynamics and Elimate Dynamics, North Holland, Amsterdam, p. 107.
Parker, E. N.: 1979, Cosmical Magnetic Fields, Clarendon Press, Oxford.
Parker, E. N.: 1987a, Astrophys. J. 312, 868.
Parker, E. N.: 1987b, Astrophys. J. 321, 989.
Parker, E. N.: 1987c, Astrophys. J. 321, 1009.
Proctor, M. R. E. and Weiss, N. O.: 1982, Rep. Prog. Phys. 45, 1317.
Ribes, E. and Leclare, F.: 1988, Geophys. Astrophys. Fluid Dyn. 41, 171.
Snodgrass, H. B. and Wilson, P. R.: 1987, Nature 328, 696.
Weiss, N. O.: 1966, Proc. Roy. Soc. A293, 310.
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Merryfield, W.J. Azimuthal convective rolls and the subsurface magnetic field. Sol Phys 128, 305–320 (1990). https://doi.org/10.1007/BF00154167
Received:
Revised:
Issue Date:
DOI: https://doi.org/10.1007/BF00154167