At the heart of all observed stellar magnetic activity lies the complex dynamical behaviour of the magnetic field in a star's interior, which forms the theme of this programme. Discussions will focus on the nonlinear interactions between turbulent convection, rotation and magnetic fields in the interiors of stars like the Sun, and will aim to confront theory with observations. Research into the magnetohydrodynamics (MHD) of stellar interiors is currently at an extremely exciting stage, with ever-improving observations posing a number of new theoretical challenges. High-resolution observations of the solar surface and solar atmosphere, both from ground-based telescopes and from space, have yielded amazingly detailed images of magnetic features and associated motions. Helioseismology has provided important information on the solar interior, particularly regarding the internal rotation rate: the unexpectedly strong shear (the tachocline) at the interface between the convection zone and the underlying radiative zone came as a surprise to theoreticians. Asteroseismology is beginning to probe the interiors of more distant stars.
Understanding the fundamental physical questions to which these observations give rise, requires a combination of computational and analytical approaches. With the advent of affordable parallel computing facilities, allied to advances in computational techniques, numerical experiments are now able, for the first time, to explore parameter regimes of astrophysical interest. These results also provide crucial input into the formulation of new and general theories, for such problems are intrinsically nonlinear and there is a strong overlap with nonlinear dynamics, including bifurcation theory and pattern formation. The programme will address all the fundamental issues, bringing together observers as well as theoreticians. Particular attention will be devoted to both small and large-scale dynamo action, to the origin and role of the tacholine and to techniques for large-scale computation in astrophysics.