Direct simulations of a supernova-driven galactic dynamo

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 action improbable. Aims. In the present work we address the issue of vertical transport, which is thought to be the key process to inhibit dynamo action in the galactic context. We aim to demonstrate that supernova driving is a powerful mechanism to amplify galactic magnetic fields. Methods. We conduct direct numerical simulations in the framework of resistive magnetohydrodynamics. Our local box model of the interstellar medium comprises optically thin radiative cooling, an external gravitational potential, and background shear. Dynamo coefficients for mean-field models are measured by means of passive test fields. Results. Our simulations show that supernova-driven turbulence in conjunction with shear leads to exponential amplification of the mean magnetic field. Turbulent pumping is found to be directed inward and is approximately balanced by a galactic wind.