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Astron. Astrophys. 333, 27-30 (1998)
Three-dimensional dynamos in spiral galaxies
R. Rohde and
D. Elstner
Astrophysikalisches Institut Potsdam, An der Sternwarte
16, D-14482 Potsdam, Germany
Received 28 October 1997 / Accepted 28 January 1998
Abstract
Solutions of the 3D nonlinear induction equation for dynamos in
spiral galaxies are presented in this paper. Our model includes
differential rotation, ambipolar diffusion and, based on small-scale
turbulence, eddy diffusivity and the tensorial ![[FORMULA]](img1.gif)
-effect underlying magnetic feedback. The nonaxisymmetric
radial-azimuthal spiral pattern and the vertical stratification of the
galaxy are represented in the density and turbulence profile.
Our calculations are chiefly concerned with the effect of field concentration between (or within) the spiral arms. The possible induction of bisymmetric instead of axisymmetric structured fields is also investigated.
We distinguish between models with weak and strong turbulence
contribution, that is small and large correlation time
![[FORMULA]](img2.gif)
of interstellar turbulence. For small
correlation times we find axisymmetric steady solutions of even parity
showing concentration between the spiral arms. The pitch angles are
relatively large and increase with enlarged correlation time. Large
correlation times are linked with oscillating BSS type solutions of
again even parity, but they are clearly concentrated within the spiral
arms.
Key words: magnetohydrodynamics
(MHD) 
turbulence
ISM: magnetic
fields
galaxies: ISM
Send offprint requests to: D. Elstner
Contents
- 1. Introduction
- 2. The mean-field electrodynamics
- 2.1. The turbulent EMF
- 2.2. Ambipolar diffusion
- 3. The model
- 3.1. Differential rotation
- 3.2. Nonaxisymmetry
- 3.3. Vertical stratification
- 4. Results
- Acknowledgements
- References
© European Southern Observatory (ESO) 1998
Online publication: April 15, 1998
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