Hostname: page-component-7bb8b95d7b-qxsvm Total loading time: 0 Render date: 2024-09-21T19:19:52.879Z Has data issue: false hasContentIssue false
  • English
  • Français

The Solar Dynamo

Published online by Cambridge University Press:  19 July 2016

D. Schmitt
D. Schmitt*
Affiliation:
Universitäts–Sternwarte, Geismarlandstr. 11 D-3400 Göttingen, Federal Republic of Germany

Abstract

Core share and HTML view are not available for this content. However, as you have access to this content, a full PDF is available via the ‘Save PDF’ action button.

The generation of the solar magnetic field is generally ascribed to dynamo processes in the convection zone. The dynamo effects, differential rotation (ω–effect) and helical turbulence (α–effect) are explained, and the basic properties of the mean–field dynamo equations are discussed in close comparison with the observed solar cycle.

Especially the question of the seat of the dynamo is addressed. Problems of a dynamo in the convection zone proper could be magnetic buoyancy, the nearly strict observance of the polarity rules and the migration pattern of the magnetic fields which are difficult to understand in the light of recent studies of the field structure in the convection zone and by observations of the solar acoustic oscillations. To overcome some of these problems it has been suggested that the solar dynamo operates in the thin overshoot region at the base of the convection zone instead. Some aspects of such an interface dynamo are discussed. As an alternative to the turbulent α–effect a dynamic α-effect based on magnetostrophic waves driven by a magnetic buoyancy instability of a magnetic flux layer is introduced. Model calculations for both pictures, a convection zone and an interface dynamo, are presented which use the internal rotation of the sun as deduced from helioseismology. Solutions with solar cycle behaviour are only obtained if the magnetic flux is bounded in the lower convection zone and the α–effect is concentrated near the equator.

Another aspect briefly addressed is the nonlinear saturation of the magnetic field. The necessity of the dynamic nature of the dynamo processes is emphasized, and different processes, e.g. magnetic buoyancy and α-quenching, are mentioned.

Keywords

Mean–Field ElectrodynamicsDynamo TheorySun
Type
1. The Solar Dynamo
Information
Symposium - International Astronomical Union , Volume 157: The Cosmic Dynamo , 1993 , pp. 1 - 12
Copyright
Copyright © Kluwer 1993 

References

Acheson, D.J.: 1978, Phil. Trans. Roy. Soc. A289, 459 Google Scholar
Acheson, D.J.: 1979, Solar Phys. 62, 23 Google Scholar
Acheson, D.J. & Hide, R.: 1973, Rep. Prog. Phys. 36, 159 CrossRefGoogle Scholar
Acheson, D.J. & Gibbons, M.P.: 1978, J. Fluid Mech. 85, 743 CrossRefGoogle Scholar
Belvedere, G., Pitadella, R.M. & Proctor, M.R.E.: 1990, Geophys. Astrophys. Fluid Dyn. 51, 263 Google Scholar
Brandenburg, A. & Tuominen, I.: 1990, ‘The Solar Dynamo’, in The Sun and Cool Stars: activity, magnetism, dynamos , Tuominen, I., Moss, D. & Rüdiger, G. (eds.), IAU-Coll. 130, Lecture Notes in Physics 380, 223 Google Scholar
Brandenburg, A., Krause, F., Meinel, R., Moss, D. & Tuominen, I.: 1989, Astron. Astrophys. 213, 411 Google Scholar
Brandenburg, A., Nordlund, Å., Pulkinnen, P., Stein, R.F. & Tuominen, I.: 1990, Astron. Astrophys. 232, 277 Google Scholar
Brandenburg, A., Moss, D., Rüdiger, G. & Tuominen, I.: 1991, Geophys. Astrophys. Fluid Dyn. 61, 179 Google Scholar
Brandenburg, A., Moss, D. & Tuominen, I.: 1992, ‘Stratification and thermodynamics in mean–field dynamos’, preprint Google Scholar
Brandenburg, A., Moss, D. & Tuominen, I.: 1992, ‘Turbulent pumping in the solar dynamo’, in NSO/Sacramento Peak 12th Summer Workshop , Harvey, K.L. (ed.), Astron. Soc. Pacific Conf. Proc. Google Scholar
Brown, T.M., Morrow, C.A.: 1987, Astrophys. J. 314, L21 Google Scholar
Brown, T.M., Christensen–Dalsgaard, J., Dziembowski, W.A., Goode, P., Gough, D.O. & Morrow, C.A.: 1989, Astrophys. J. 343, 526 Google Scholar
Choudhuri, A.R.: 1990, Astrophys. J. 355, 733 Google Scholar
Choudhuri, A.R.: 1992, Astron. Astrophys. 253, 277 Google Scholar
DeLuca, E.E. & Gilman, P.A.: 1986, Geophys. Astrophys. Fluid Dyn. 37, 85 Google Scholar
DeLuca, E.E. & Gilman, P.A.: 1988, Geophys. Astrophys. Fluid Dyn. 43, 119 Google Scholar
DeLuca, E.E. & Gilman, P.A.: 1991, ‘The Solar Dynamo’, in The Solar Atmosphere and Interior , Cox, A.N. (ed.), Univ. of Arizona Press, Tucson Google Scholar
DeVore, C.R. & Sheeley, N.R. Jr.: 1987, Solar Phys. 108, 47 Google Scholar
Drobyshevski, E.M. & Yuferev, V.S.: 1974, J. Fluid Mech. 65, 33 CrossRefGoogle Scholar
Durney, B.R., DeYoung, D.S. & Roxburgh, I.W.: 1993, ‘On the generation of the large–scale and turbulent magnetic fields in solar–type stars’, Solar Phys. , in press Google Scholar
Dziembowksi, W.A., Goode, P.R. & Libbrecht, K.G.: 1989, Astrophys. J. 337, L53 Google Scholar
Elstner, D. & Rüdiger, G.: 1993, ‘Stellar dynamos with anisotropic α-tensor’, this volume Google Scholar
Fearn, D.R. & Proctor, M.R.E.: 1984, Phys. Earth Planet. Inter. 36, 78 Google Scholar
Fearn, D.R. & Proctor, M.R.E.: 1987, J. Fluid Mech. 178, 521 Google Scholar
Ferrière, K.: 1992, ‘The Full Alpha–Tensor Due to Supernova Explosions and Superbubbles in the Galactic Disk’, preprint Google Scholar
Ferriz–Mas, A., Schüssler, M.: 1992, ‘Instabilites of magnetic flux tubes in a stellar convection zone. I: Toroidal flux tubes in differentially roatating stars’, preprint Google Scholar
Galloway, D.J. & Weiss, N.O.: 1981, Astrophys. J. 243, 945 Google Scholar
Gilman, P.A.: 1983, Astrophys. J. Suppl. 53, 243 Google Scholar
Gilman, P.A., Miller, J.: 1981, Astrophys. J. Suppl. 46, 211 Google Scholar
Gilman, P.A., Miller, J.: 1986, Astrophys. J. Suppl. 61, 585 Google Scholar
Gilman, P.A., Morrow, C.A. & DeLuca, E.E.: 1989, Astrophys. J. 338, 528 Google Scholar
Glatzmaier, G.A.: 1984, J. Comp. Phys. 55, 461 Google Scholar
Glatzmaier, G.A.: 1985a, Astrophys. J. 291, 300 CrossRefGoogle Scholar
Glatzmaier, G.A.: 1985b, Geophys. Astrophys. Fluid Dyn. 31, 137 CrossRefGoogle Scholar
Gokhale, M.H. & Javaraiah, J.: 1990, Mon. Not. Royal Astron. Soc. 243, 241 Google Scholar
Gokhale, M.H. & Javaraiah, J.: 1992, Solar Phys. 138, 399 Google Scholar
Gokhale, M.H., Javaraiah, J. & Hiremath, K.M.: 1990, in Solar Photosphere: Structure, Convection and Magnetic Fields , Stenflo, J.O. (ed.), IAU–Symp. 138, 375 Google Scholar
Gokhale, M.H., Javaraiah, J., Kutty, K. Narayanan & Varghese, B.A.: 1992, Solar Phys. 138, 35 Google Scholar
Golub, L., Rosner, R., Vaiana, G.S. & Weiss, N.O.: 1981, Astrophys. J. 243, 309 Google Scholar
Hellmich, R.: 1978, Geophys. Astrophys. Fluid Dyn. 10, 89 Google Scholar
Hinata, S.: 1982, Astrophys. J. 256, L23 Google Scholar
Howard, R.F. & LaBonte, B.J.: 1980, Astrophys. J. 239, L33 Google Scholar
Howard, R.F. & LaBonte, B.J.: 1991, Solar Phys. 74, 131 Google Scholar
Hoyng, P.: 1987, Astron. Astrophys. 171, 348 and 357 Google Scholar
Hoyng, P.: 1988, Astrophys. J. 332, 857 Google Scholar
Hoyng, P.: 1990, ‘Excitation of Dynamo Waves’, in Solar Photosphere: Structure, Convection and Magnetic Fields , Stenflo, J.O. (ed.), IAU-Symp. 138, 359 Google Scholar
Hughes, D.W.: 1991, ‘Magnetic Buoyancy’, in Advances in Solar System Magnetohydrodynamics , Priest, E.R. & Wood, A.W. (eds.), Cambridge University Press, p. 77 Google Scholar
Jennings, R.L. & Weiss, N.O.: 1991, Mon. Not. R. Astr. Soc. 252, 249 Google Scholar
Kichatinov, L.L.: 1991, Astron. Astrophys. 243, 483 Google Scholar
Köhler, H.: 1973, Astron. Astrophys. 25, 467 Google Scholar
Krause, F. & Rädler, K.–H.: 1980, Mean–Field Magnetohydrodynmics and Dynamo Theory , Pergamon Press, Oxford Google Scholar
Kurths, J., Feudel, U. & Brandenburg, A.: 1993, ‘Inhomogeneous chaos in nonlinear dynamo models’, this volume Google Scholar
Leighton, R.B.: 1969, Astrophys. J. 156, 1 Google Scholar
Leroy, J.–L. & Noens, J.–C.: 1983, Astron. Astrophys. 120, L1 Google Scholar
Libbrecht, K.G.: 1988, ‘Solar p–mode frequency split tings’, in Seismology of the Sun and Sun–Like Stars , Rolfe, E.J. (ed.), ESA SP–286, p. 131 Google Scholar
Makarov, V.I. & Makarova, V.V.: 1986, J. Astrophys. Astron. 7, 113 Google Scholar
Malkus, W.V.R. & Proctor, M.R.E.: 1975, J. Fluid Mech. 67, 417 Google Scholar
Meinel, R. & Brandenburg, A.: 1990, Astron. Astrophys. 238, 369 Google Scholar
Moffatt, H.K.: 1978, Magnetic Field Generation in Electrically Conducting Fluids , Cambridge University Press Google Scholar
Moreno–Insertis, F.: 1983, Astron. Astrophys. 122, 241 Google Scholar
Moreno–Insertis, F.: 1986, Astron. Astrophys. 166, 291 Google Scholar
Moreno–Insertis, F., Ferriz–Mas, A. & Schüssler, M.: 1992, ‘Storage of magnetic flux tubes in a convective overshoot region’, Astron. Astrophys. , in press Google Scholar
Moss, D., Brandenburg, A., Tavakol, R. & Tuominen, I.: 1992, ‘Stochastic effects in mean field dynamos’, preprint Google Scholar
Moss, D., Tuominen, I. & Brandenburg, A.: 1990a, Astron. Astrophys. 228, 284 Google Scholar
Moss, D., Tuominen, I. & Brandenburg, A.: 1990b, Astron. Astrophys. 240, 142 Google Scholar
Parker, E.N.: 1955, Astrophys. J. 122, 293 Google Scholar
Parker, E.N.: 1975, Astrophys. J. 198, 205 Google Scholar
Parker, E.N.: 1979, Cosmical Magnetic Fields , Clarendon Press, Oxford Google Scholar
Pitadella, R.M. & Stix, M.: 1986, Astron. Astrophys. 157, 338 Google Scholar
Prautzsch, T.: 1990, ‘Der Einfluß von breitenabhängigen Induktionseffekten auf einen eindimensionalen sphärischen αω–Dynamo’, Diplomarbeit, Universität Göttingen Google Scholar
Prautzsch, T.: 1993, ‘The Dynamo Mechanism in the Deep Convection Zone of the Sun’, in NATO ASI Theory of Solar and Planetary Dynamos , Proceedings of the Isaac Newton Institute, Cambridge Google Scholar
Prautzsch, T., Schmitt, D. & Schüssler, M: 1993, ‘Non-linear dynamos. II. Two-dimensional model of an overshoot layer dynamo’, in preparation Google Scholar
Proctor, M.R.E.: 1977, J. Fluid Mech. 80, 769 Google Scholar
Proctor, M.R.E. & Weiss, N.O.: 1982, Rep. Prog. Phys. 45, 1317 Google Scholar
Rädler, K.–H.: 1968, Zs. Naturforsch. 23a, 1851 Google Scholar
Rädler, K.–H.: 1980, Astron. Nachr. 301, 101 Google Scholar
Rädler, K.–H.: 1990, ‘The Solar Dynamo’, in Inside the Sun , Berthomieu, G. & Cribier, M. (eds.), Kluwer, Dordrecht, IAU-Coll 21, 385 Google Scholar
Rädler, K.–H., Wiedemann, E., Brandenburg, A., Meinel, R. & Tuominen, I.: 1990, Astron. Astrophys. 239, 413 Google Scholar
Robinson, R.D. & Durney, B.R.: 1982, Astron. Astronphys. 108, 322 Google Scholar
Rüdiger, G.: 1978, Astron. Nachr. 299, 217 Google Scholar
Rüdiger, G.: 1989, Differential Rotation and Stellar Convection , Akademie–Verlag Berlin Google Scholar
Rüdiger, G. & Kichatinov, L.L.: 1990, Astron. Astrophys. 236, 503 Google Scholar
Rüdiger, G. & Kichatinov, L.L.: 1992, ‘Alpha–effect and alpha–quenching’, preprint Google Scholar
Rüdiger, G., Tuominen, I., Krause, F. & Virtanen, H.: 1986, Astron. Astrophys. 166, 306 Google Scholar
Schmalz, S. & Stix, M.: 1991, Astron. Astrophys. 245, 654 Google Scholar
Schmitt, D.: 1984, ‘Dynamo Action of Magnetostrophic Waves’, in The Hydromagnetics of the Sun , Guyenne, T.D., Hunt, J.J. (eds.), ESA SP–220, 223 Google Scholar
Schmitt, D.: 1985, ‘Dynamowirkung magnetostrophischer Wellen’, Thesis, Universität Göttingen Google Scholar
Schmitt, D.: 1987, Astron. Astrophys. 174, 281 Google Scholar
Schmitt, D. & Schüssler, M.: 1989, Astron. Astrophys. 223, 343 Google Scholar
Schmitt, D.: 1993, ‘Inversion approach to the solar dynamo’, in preparation Google Scholar
Schmitt, D.: 1993, ‘The influence of turbulent diamagnetism and topological pumping on an αω–dynamo in the deep convection zone of the sun’, in preparation Google Scholar
Schmitt, J.H.M.M., Rosner, R. & Bohn, H.U.: 1984, Astrophys. J. 282, 316 Google Scholar
Schou, J., Christen–Dalsgaard, J. & Thompson, M.J.: 1992, Astrophys. J. 385, L59 Google Scholar
Schüssler, M.: 1977, Astron. Astrophys. 56, 439 Google Scholar
Schüssler, M.: 1979a, Astron. Astrophys. 71, 79 Google Scholar
Schüssler, M.: 1979b, Astron. Astrophys. 72, 348 Google Scholar
Schüssler, M.: 1980, Nature 288, 150 Google Scholar
Schüssler, M.: 1981, Astron. Astrophys. 94, L17 Google Scholar
Schüssler, M.: 1983, ‘Stellar Dynamo Theory’, in Solar and Stellar Magnetic Fields: Origins and Coronal Effects , Stenflo, J.O. (ed.), IAU–Symp. 102, 213 Google Scholar
Schüssler, M.: 1984, ‘On the Structure of Magnetic Fields in the Solar Convection Zone’, in The Hydromagnetics of the Sun Guyenne, T.D., Hunt, J.J. (eds.), ESA SP–220, 67 Google Scholar
Schüssler, M.: 1987, ‘Magnetic Fields and the Rotation of the Solar Convection Zone’, in The Internal Solar Angular Velocity , Durney, B.R. & Sofia, S. (eds.), Reidel, Dordrecht, p. 303 Google Scholar
Schüssler, M.: 1990, ‘Comments on the structure and dynamics of magnetic fields in stellar convection zones’, Habilitationschrift, Universität Göttingen Google Scholar
Schüssler, M., Ferriz-Mas, A. & Schmitt, D.: 1993, ‘An α–effect due to flux tube instabilities in the solar convection zone’, in preparation Google Scholar
Sheeley, N.R., Nash, A.G. & Wang, Y.–M.: 1987, Astrophys. J. 319, 481 Google Scholar
Skaley, D. & Stix, M.: 1991, Astron. Astrophys. 241, 227 Google Scholar
Spiegel, E.A. & Weiss, N.O.: 1980, Nature 287, 616 Google Scholar
Spruit, H.C. & van Ballegooijen, A.A.: 1982, Astron. Astrophys. 106, 58 Google Scholar
Steenbeck, M. & Krause, F.: 1969, Astron. Nachr. 291, 49 Google Scholar
Steenbeck, M., Krause, F. & Rädler, K.–H.: 1966, Z. Naturforsch. 21a, 369 CrossRefGoogle Scholar
Stenflo, J.O.: 1973, Solar Phys. 32, 41 Google Scholar
Stenflo, J.O.: 1988, Astrophys. Space Sci. 144, 321 Google Scholar
Stenflo, J.O. & Güdel, M.: 1988, Astron. Astrophys. 191, 137 Google Scholar
Stenflo, J.O. & Vogel, M.: 1986, Nature 319, 285 Google Scholar
Stenflo, J.O. & Weisenhorn, A.L.: 1987, Solar Phys. 108, 205 Google Scholar
Stix, M.: 1974, Astron. Astrophys. 37, 121 Google Scholar
Stix, M.: 1976, Astron. Astrophys. 47, 243 Google Scholar
Stix, M.: 1987, ‘On the Origin of Stellar Magnetism’, in Solar and Stellar Physics, Schröter, E.–H. & Schüssler, M. (eds.), Lecture Notes in Physics , 292, 15 Google Scholar
Stix, M.: 1991, Geophys. Astrophys. Fluid Dyn. 62, 211 Google Scholar
Teuben, L., Hoyng, P. & Schmitt, D.: 1993, ‘Periodicities in the Large–Scale Solar Magnetic Field’, in preparation Google Scholar
Topka, K., Moore, R., LaBonte, B.J. & Howard, R.: 1982, Solar Phys. 79, 231 Google Scholar
Tsinganos, K.C.: 1980, Astrophys. J. 239, 746 Google Scholar
van Ballegooijen, A.A.: 1982, Astron. Astrophys. 113, 99 Google Scholar
van Ballegooijen, A.A.: 1983, Astron. Astrophys. 118, 275 Google Scholar
van Ballegooijen, A.A. & Choudhuri, A.R.: 1988, Astrophys. J. 333, 965 Google Scholar
Wädler, M., Deinzer, W. & Stix, M.: 1980, J. Fluid Mech. 96, 207 Google Scholar
Wang, Y.–M., Sheeley, N.R. & Nash, A.G.: 1991, Astrophys. J. 383, 431 Google Scholar
Weiss, N.O.: 1989, ‘Dynamo Processes in Stars’, in Accretion Discs and Magnetic Fields in Astrophysics , Belvedere, G. (ed.), Kluwer, Dordrecht, p. 11 Google Scholar
Weiss, N.O.: 1990, Phil. Trans. R. Soc. Lond. A330, 617 Google Scholar
Weiss, N.O., Cattaneo, F. & Jones, C.A.: 1984, Geophys. Astrophys. Fluid Dyn. 30, 305 Google Scholar
Weisshaar, E.: 1982, Geophys. Astrophys. Fluid Dyn. 21, 285 Google Scholar
Yoshimura, H.: 1972, Astrophys. J. 178, 863 Google Scholar
Yoshimura, H.: 1975, Astrophys. J. 201, 740 Google Scholar
Yoshimura, H.: 1978, Astrophys. J. 220, 692 Google Scholar
Yoshimura, H.: 1981, Astrophys. J. 247, 1102 Google Scholar
Zel'dovich, Ya.B.: 1956, Sov. Phys. JETP 31, 154 Google Scholar