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Context. Supernovae are known to be the dominant energy source for driving turbulence in the interstellar medium. Yet their effect on magnetic field amplification in spiral galaxies is still poorly understood. Analytical models based on the evolution of isolated, non-interacting supernova remnants predicted a dominant vertical pumping rendering dynamo… (More)

- K Otmianowska-Mazur, G R Udiger, D Elstner, R Arlt
- 1997

Following earlier suggestions to replace the ensemble average used in the mean-eld electrodynamics by an averaging over the azimuthal coordinate we consider the basic coeecients in the turbulent electromotive force (EMF) as time-dependent functions. The well-known coeecients and T { both in the relevant tensorial formulations { are derived from one and the… (More)

- G Rüdiger, D Elstner, M Ossendrijver
- 2002

The question is answered whether α 2-shell-dynamos are able to produce a cyclic activity or not. Only kinematic dynamos are considered and only the solutions with the lowest dynamo number are studied without restrictions about the axial symmetry of the solution. The α-effect is allowed to be latitudinally inhomogeneous and/or anisotropic, but it is assumed… (More)

- M V Rekowski, D Elstner
- 1999

The influence of large-scale magnetic fields on the structure of accretion disks is studied. The magnetic field is obtained by a self-consistent nonlinear dynamo model with magnetic pressure strongly influencing the density stratifica-tion which itself feeds back to the field generation. The resulting magnetic field geometry is discussed in relation to the… (More)

- D. Elstner, K. Otmianowska-Mazur, S. von Linden, M. Urbanik
- 2000

We investigate the evolution of three-dimensional (3D), large-scale galactic magnetic fields under the influence of time dependent gas flows in spiral arms and excited by a turbulent dynamo. Our principal goal is to check how the enhanced turbulent diffusion in spiral arms affects the global magnetic field structure evolving under the influence of the… (More)

We consider the effect of toroidal magnetic fields on hydrodynamically stable Taylor-Couette differential rotation flows. For current-free magnetic fields a nonaxisymmetric m = 1 magne-torotational instability arises when the magnetic Reynolds number exceeds O(100). We then consider how this 'azimuthal magnetorotational instability' (AMRI) is modified if… (More)

Recent simulations of supernova-driven turbulence within the ISM support the existence of a large-scale dynamo. With a growth time of about two hundred million years, the dynamo is quite fast – in contradiction to many assertions in the literature. We here present details on the scaling of the dynamo effect within the simulations and discuss global… (More)

- R. Rohde, R. Beck, D. Elstner
- 1999

Dynamo models for the structure of the regular magnetic field in the galaxy NGC 6946 are confronted with recent observations of polarized radio emission at λ3.5 cm. The observed behaviour of the concentration of regular fields between the gaseous spiral arms (" magnetic spiral arms ") is achieved via a non-axisymmetric azimuthal distribution of only the… (More)

3 S u m m a r y : We present simulations of the 3D nonlinear induction equation in order to investigate the temporal evolution of large-scale magnetic elds in spiral galaxies. Our model includes diierential rotation, ambipolar diiusion and, based on small-scale turbulence, eddy diiusivity and the tensorial-eeect with magnetic feedback. The nonax-isymmetric… (More)

- A Bonanno, D Elstner, G Rüdiger, G Belvedere
- 2008

We have developed a high-precision code which solves the kinematic dynamo problem both for given rotation law and meridional flow in the case of a low eddy diffusivity of the order of 10 11 cm 2 /s known from the sunspot decay. All our models work with an α-effect which is positive (negative) in the northern (southern) hemisphere. It is concentrated in… (More)