Hostname: page-component-586b7cd67f-2brh9 Total loading time: 0 Render date: 2024-11-24T20:46:52.886Z Has data issue: false hasContentIssue false
  • English
  • Français

The Galactic Dynamo: Modes and Models

Published online by Cambridge University Press:  19 July 2016

G. Rüdiger ,
D. Elstner  and
M. Schultz
G. Rüdiger
Affiliation:
Astrophysikalisches Institut Potsdam An der Sternwarte 16, D-O-1590 Potsdam, Germany
D. Elstner
Affiliation:
Astrophysikalisches Institut Potsdam An der Sternwarte 16, D-O-1590 Potsdam, Germany
M. Schultz
Affiliation:
Astrophysikalisches Institut Potsdam An der Sternwarte 16, D-O-1590 Potsdam, 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 hitherto known essentials of the present-day dynamo theory of the galactic magnetic fields are reported. The vertical stratification of the interstellar turbulence is exclusively considered as the source of the α-effect. New expressions for this tensorial effect and its quenching by the field are applied. Although its anisotropy and the influence of the halo easily yield the excitation of non-axisymmetric magnetic configurations of diverse equatorial symmetry, the galactic differential rotation finally leads to axisymmetric and quadrupolar solutions. The magnetic strength of the dynamo fields slightly exceeds the equipartition value while its angular momentum transport (into the intergalactic space) is very small.

For increasingly steep vertical gradients of the turbulence intensity a saturation of the field strength is found since the eddy diffusivity grows with the α-effect. Only beyond the maximum of the field the equatorial symmetry changes to an equatorial antisymmetry, i.e. to dipolar solutions.

In order to produce the observed values of the pitch angles one has only to choose correlation times of the turbulence slightly exceeding the usually accepted 107 yrs.

Type
8. Magnetic Fields in Galaxies: Dynamo Theory
Information
Symposium - International Astronomical Union , Volume 157: The Cosmic Dynamo , 1993 , pp. 321 - 331
Copyright
Copyright © Kluwer 1993 

References

Beck, R.: 1993, these proceedings ,Google Scholar
Brandenburg, A., Tuominen, I., Moss, D.: 1989, Geophys. Astrophys. Fluid Dyn. 49, 129 CrossRefGoogle Scholar
Brandenburg, A., Nordlund, A., Pulkkinen, P., Stein, R.F., Tuominen, I.: 1990, Astron. Astrophys. 232, 277 Google Scholar
Brandenburg, A., Donner, K.J., Moss, D., Shukurov, A.A., Sokoloff, D.D., Tuominen, I.: 1993, preprint ,Google Scholar
Deinzer, W., Grosser, H., Schmitt, D.: 1993, Astron. Astrophys. , sub. Google Scholar
Donner, K.J., Brandenburg, A.: 1990, Astron. Astrophys. 240, 289 Google Scholar
Elstner, D., Meinel, R., Rüdiger, G.: 1990, Geophys. Astrophys. Fluid Dyn. 50, 85 CrossRefGoogle Scholar
Elstner, D., Meinel, R., Beck, R.: 1992, Astron. Astrophys. Suppl. 94, 587 Google Scholar
Ferrière, K.: 1992, Astrophys. J. 389, 286 CrossRefGoogle Scholar
Ferrière, K.: 1992, Astrophys. J. 391, 188 CrossRefGoogle Scholar
Gilbert, A.D., Sulem, P.-L.: 1990, Geophys. Astrophys. Fluid Dyn. 51, 243 CrossRefGoogle Scholar
Kaisig, M., Rüdiger, G., Yorke, H.W.: 1993, Astron. Astrophys. ,Google Scholar
Kichatinov, L.L.: 1987, Geophys. Astrophys. Fluid Dyn. 38, 273 CrossRefGoogle Scholar
Kichatinov, L.L.: 1991, Astron. Astrophys. 243, 483 Google Scholar
Kichatinov, L.L., Rüdiger, G.: 1992, Astron. Astrophys. 260, 494 Google Scholar
Krause, F., Meinel, R.: 1988, Geophys. Astrophys. Fluid Dyn. 43, 95 CrossRefGoogle Scholar
Krause, F., Rädler, K.-H.: 1981, Mean-field magnetohydrodynamics and dynamo theory , Pergamon Google Scholar
Krause, F., Meinel, R., Elstner, D., Rüdiger, G.: 1990, in: R. Beck et al. (eds.): Galactic and Intergalactic Magnetic Fields, IAU No. 140, 97 CrossRefGoogle Scholar
Krause, M., Beck, R., Hummel, E.: 1989, Astron. Astrophys. 217, 17 Google Scholar
Meinel, R., Elstner, D., Rüdiger, G.: 1990, Astron. Astrophys. 236, L33 Google Scholar
Moffatt, H.K.: 1970, J. Fluid Mech. 44, 705 CrossRefGoogle Scholar
Moss, D., Brandenburg, A.: 1992, Astron. Astrophys. 256, 371 Google Scholar
Roberts, P.H., Soward, A.: 1975, Astron. Nachrichten 296, 49 CrossRefGoogle Scholar
Rüdiger, G.: 1980, Astron. Nachrichten 299, 217 CrossRefGoogle Scholar
Rüdiger, G.: 1990, Geophys. Astrophys. Fluid Dyn. 50, 53 CrossRefGoogle Scholar
Rüdiger, G., Kichatinov, L.L.: 1993, Astron. Astrophys. 269, 581 Google Scholar
Rüdiger, G., Elstner, D.: 1993, Astron. Astrophys. acc.,Google Scholar
Rüdiger, G., Elstner, D., Schultz, M.: 1993, Astron. Astrophys. acc.,Google Scholar
Schmitt, D.: 1990, Reviews in modern astronomy 3, 88 Google Scholar
Sofue, Y., Fujimoto, M., Wielebinski, R.: 1988, Ann. Rev. Astron. Astrophys. 24, 459 CrossRefGoogle Scholar
Steenbeck, M., Krause, F., Rädler, K.-H.: 1966, Z. Naturforsch. 21a, 369 CrossRefGoogle Scholar
Stepinski, T.F., Levy, E.H.: 1988, Astrophys. J. 331, 416 CrossRefGoogle Scholar
Wälder, M., Deinzer, W., Stix, M.: 1980, J. Fluid Mech. 96, 207 CrossRefGoogle Scholar