It is argued that the seed field from the galactic dynamo comes from the first supernovae or stellar winds, or perhaps from early AGNs.

The state of the art for dynamo models in spiral galaxies is reviewed. The comparison of numerical models with special properties of observed magnetic fields yields constraints for the turbulent diffusivity and the α-effect. The derivation of the turbulence parameters from the vertical structure of the interstellar medium gives quite reasonable values for modelling the regular magnetic fields in galaxies with an α2Ω-dynamo. Considering the differences of the turbulence between spiral arms and interarm regions, the observed interarm magnetic fields are recovered in the numerical models due to the special properties of the α2Ω-dynamo.

We argue that interstellar gas in elliptical galaxies can be turbulent, with turbulent scale and velocity of 400 pc and 20 km s−1 respectively. An upper limit on turbulent velocity, ≃ 50 km s−1, follows from the requirement that the turbulence dissipation rate does not exceed the X-ray gas luminosity. The turbulence can generate random magnetic fields of 0.3 μG strength at the above scale via fluctuation dynamo action. The resulting Faraday rotation is random, with a typical value of 5-30 rad m−2, consistent with observational evidence available.

Galactic magnetic fields are, typically, modelled by mean-field dynamos involving the α-effect. Here we consider, very briefly, some of the issues involving the nonlinear dependence of α on the mean field.

Mean field dynamos may explain the origin of large scale magnetic fields of galaxies, but controversy arises over the extent of dynamo quenching by the growing field. Here we explain how apparently conflicting results may be mutually consistent, by showing the role of magnetic helicity conservation and boundary terms usually neglected. We estimate the associated magnetic energy flowing out of the Galaxy but emphasize that the mechanism of field escape needs to be addressed.

Using a closure model for the evolution of magnetic correlations, we uncover an interesting plausible saturated state of the small-scale fluctuation dynamo (SSD) and a novel anology between quantum mechanical tunnelling and the generation of large-scale fields. Large scale fields develop via the α-effect, but as magnetic helicity can only change on a resistive timescale, the time it takes to organize the field into large scales increases with magnetic Reynolds number. This is very similar to the results which obtain from simulations using the full MHD equations.

Using a periodic box calculation it is shown that, owing to helicity conservation, a large scale field can only develop on a resistive timescale. This behaviour can be reproduced by a mean-field dynamo with α and ƞt quenchings that are equally strong and ‘catastrophic’.

A Special Session was held during the XXIV General Assembly on the topic “Astronomy for Developing Countries”. During two-and-a-half days, thirty-eight oral papers were presented and a similar number of poster papers were displayed. Edited summaries of the oral papers are presented here. Full texts of those papers and abstracts of the posters appear in a separate volume published in 2001 by the ASP.