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An Isaac Newton Institute Workshop

MAGNETOHYDRODYNAMICS OF STELLAR INTERIORS <br> Supported by the European Commission, Sixth Framework Programme - <br> Marie Curie Conferences and Training Courses - MSCF-CT-2003-503674

Decay of a simulated bipolar magnetic field in the solar surface layers

Authors: A. Voegler (Max-Planck-Institut fuer Aeronomie, Katlenburg-Lindau, Germany), R. Cameron (Max-Planck-Institut fuer Aeronomie, Katlenburg-Lindau, Germany), C.U. Keller (National Solar Observatory, Tucson, USA), M. Schuessler (Max-Planck-Institut fuer Aeronomie, Katlenburg-Lindau, Germany)

Abstract

Using MURaM - a MHD code designed for applications in the solar photosphere and convection zone, we have studied the evolution of a mixed-polarity magnetic field in the surface layers of the Sun. The simulations, which have a horizontal extent of 6 Mm x 6 Mm and contain the visible surface around optical depth unity, include a detailed treatment of non-local radiative transfer effects in the photosphere in order to allow a direct comparison with observations. We discuss the time-evolution of magnetic structures and their statistical properties, present details of the flux-cancellation process and comment on its signatures in simulated observations of our numerical model. We show that the rate at which the field decays is consitent with the expected turbulent decay time scale and discuss the dependence of the decay rate on the initial conditions.