Magnetic Fields in Galaxies

Aim of the workshop

The purpose of this workshop is to better understand magnetic fields in galaxies: to define what we think is well-established, and to define how to move forward on those questions which have no satisfactory answer at present. In particular, the workshop aims to bring together and compare observations, numerical simulations and analytical theory on galactic magnetic fields.

The following subjects will be covered by the programme:

1. Magnetic fields in external galaxies 2. Magnetic fields in our own Galaxy 3. Models of the (warm) turbulent ISM 4. Origin and evolution of galactic magnetic fields

Structure of the Workshop

The format of the workshop will be a mix of prepared contributions from the participants (mostly short ones of about 15 mins), and broad discussions in which several central questions can be debated. Every attempt should be made to discuss the theoretical and observational aspects side-by-side, so that we can try to agree on what is observed, and how the observations can be understood in terms of the theoretical frame-work. Equally important will be to identify where there is no agreement on what is observed, or predicted, or where the interpretation is not clear, or the prediction ambiguous. Finally, discussion may help to identify ways to resolve discrepancies, lack of understanding etc.

Programme

We think that the four areas indicated above can be addressed most effectively by defining several questions that we would like answered by the end of the Workshop. Clearly, the questions can be divided into subject areas, but there are so many relationships between the subject areas that we would like to build the Workshop primarily around a set of questions. Below we have listed a few of the more obvious questions, without attempting to be complete. In the next month, we will put together a more detailed programme on the basis of input from the participants.

The large-scale magnetic field

What are the predictions of the current best models for their origin, evolution and the time-scales involved ? What determines the strengths of the large- (and small-)scale fields in the models, and how does that compare to the observed values ? Is there evidence for field asymmetries w.r.t. the galactic plane ? Field reversals; are they real and, if so, what is their scale and origin ? How do the field and the gas flow interact, and what do the observations and models tell us about that interaction ? How well are the fields aligned with the spiral arms, and how is does alignment come about ? What do we know about the magnetic field in the halo, and its connection to the field in the disk ? What is the connection with the intergalactic (or cluster) field ?

The field and its interaction with the ISM

What are the predictions for the interaction between dynamo's and ISM-physics ? How can we best observe the results of the interaction between dynamo's and ISM-physics ? How do the energy input into the turbulent ISM, and the decay and build-up of the field compare ? Is energy balance between the field and any of the other ISM components and cosmic rays predicted, and what do the observations tell us ? How well is the field coupled to the plasma ? How do we best determine the properties of the small-scale field (Faraday tomography, 'canals', etc.) ? How ubiquitous is turbulence in the warm ISM and what are its characteristics and typical scales ?

The way forward

What new instruments and techniques will and/or should become available ? What are the crucial experiments to test the models ? How can/must models be improved ?

Coordinators: Peter Katgert (Leiden, NL) Rainer Beck (Bonn, Germany) Ger de Bruyn (Groningen and Dwingeloo, NL) Marijke Haverkorn (Harvard, USA) Fabian Heitsch (Munich, Germany) Tom Landecker (Penticton, Canada) Anvar Shukurov (Newcastle, UK)