Hostname: page-component-586b7cd67f-2plfb Total loading time: 0 Render date: 2024-11-26T13:20:29.019Z Has data issue: false hasContentIssue false
  • English
  • Français

Filaments and the Solar Dynamo

Published online by Cambridge University Press:  12 April 2016

N. Seehafer
N. Seehafer*
Affiliation:
Institut für Physik, Universität Potsdam, PF 601553, D-14415 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.

Filaments are a global phenomenon and their formation, structure and dynamics are determined by magnetic fields. So they are an important signature of the solar magnetism. The central mechanism in traditional mean-field dynamo theory is the alpha effect and it is a major result of this theory that the presence of kinetic or magnetic helicities is at least favourable for the effect. Recent studies of the magnetohydrodynamic equations by means of numerical bifurcation-analysis techniques have confirmed the decisive role of helicity for a dynamo effect. The alpha effect corresponds to the simultaneous generation of magnetic helicities in the mean field and in the fluctuations, the generation rates being equal in magnitude and opposite in sign. In the case of statistically stationary and homogeneous fluctuations, in particular, the alpha effect can increase the energy in the mean magnetic field only under the condition that also magnetic helicity is accumulated there. Generally, the two helicities generated by the alpha effect, that in the mean field and that in the fluctuations, have either to be dissipated in the generation region or to be transported out of this region. The latter may lead to the appearance of helicity in the atmosphere, in particular in filaments, and thus provide valuable information on dynamo processes inaccessible to in situ measurements.

Type
Global Patterns
Information
International Astronomical Union Colloquium , Volume 167: New Perspectives on Solar Prominences , 1998 , pp. 406 - 414
Copyright
Copyright © Astronomical Society of the Pacific 1998

References

Abramenko, V.I., Wang, T. and Yurchishin, V.B. 1996, Solar. Phys., 168, 75 Google Scholar
Christensen-Dalsgaard, J. and Schou, J. 1988, in Seismology of the Sun and Sun-like Stars, Domingo, V. and Rolfe, E.J. (eds.), ESA SP-286, p. 385 Google Scholar
Dombre, T., Frisch, U., Greene, J.M., Hénon, M., Mehr, A. and Soward, A.M. 1986, J. Fluid Mech., 167, 353 CrossRefGoogle Scholar
Feudel, F., Seehafer, N. and Schmidtmann, O. 1995, Phys. Lett. A, 202, 73 CrossRefGoogle Scholar
Feudel, F. et al. 1996, Phys. Rev. E, 54, 2589 Google Scholar
Frisch, U. et al. 1975, J. Fluid Mech., 68, 769 CrossRefGoogle Scholar
Galanti, B., Sulem, P.L. and Pouquet, A. 1992, Geophys. Astrophys. Fluid Dyn., 66, 183 CrossRefGoogle Scholar
Glatzmaier, G.A. 1984, J. Comp. Phys., 55, 461 Google Scholar
Glatzmaier, G.A. 1985, Geophys. Astrophys. Fluid Dyn., 31, 137 Google Scholar
Keinigs, R.K. 1983, Phys. Fluids, 26, 2558 Google Scholar
Keinigs, R. and Gerwin, A. 1986, IEEE Trans. Plasma Sci., PS-14, 858 CrossRefGoogle Scholar
Krause, F. and Rädler, K.-H. 1980, Mean-Field Magnetohydrodynamics and Dynamo Theory, Akademie-Verlag, Berlin Google Scholar
Matthaeus, W.H., Goldstein, M.L. and Lantz, S.R. 1986, Phys. Fluids, 29, 1504 Google Scholar
Meneguzzi, M. and Pouquet, A. 1989, J. Fluid Mech., 205, 297 Google Scholar
Meneguzzi, M., Frisch, U. and Pouquet, A. 1981, Phys. Rev. Lett., 47, 1060 Google Scholar
Pevtsov, A.A., Canfield, R.C. and Metcalf, T.R. 1995, ApJ, 440, L109 CrossRefGoogle Scholar
Pouquet, A., Frisch, U. and Léorat, J. 1976, J. Fluid Mech., 77, 321 Google Scholar
Radier, K.-H. and Seehafer, N. 1990, in Topological Fluid Mechanics, Moffatt, H.K. and Tsinober, A. (eds.), Cambridge Univ. Press, Cambridge, p. 157 Google Scholar
Rädler, K.-H. et al. 1990, A&A, 239, 413 Google Scholar
Rust, D.M. 1994, Geophys. Res. Lett., 21, 241 Google Scholar
Rust, D.M. and Kumar, A. 1994, Solar Phys., 155, 69 Google Scholar
Schmidtmann, O., Feudel, F. and Seehafer, N. 1997, Int. J. Bifurcation and Chaos 7(9), in pressGoogle Scholar
Seehafer, N. 1990, Solar Phys., 125, 219 Google Scholar
Seehafer, N. 1994a, A&A, 284, 593 Google Scholar
Seehafer, N. 1994b, Europhys. Lett., 27, 353 CrossRefGoogle Scholar
Seehafer, N. 1996, Phys. Rev. E, 53, 1283 CrossRefGoogle Scholar
Seehafer, N., Feudel, F. and Schmidtmann, O. 1996, A&A, 314, 693 Google Scholar
Stribling, T. and Matthaeus, W.H. 1990, Phys. Fluids B, 2, 1979 Google Scholar
Stribling, T. and Matthaeus, W.H. 1991, Phys. Fluids B, 3, 1848 Google Scholar