A&a Manuscript No. Three Dimensional Dynamos in Spiral Galaxies

Solutions of the 3D nonlinear induction equation for dynamos in spiral galaxies are presented in this paper. Our model includes diierential rotation, ambipolar diiusion and, based on small-scale turbulence, eddy diiu-sivity and the tensorial {eeect underlying magnetic feedback. The nonaxisymmetric radial-azimuthal spiral pattern and the vertical stratiication of the galaxy are represented in the density and turbulence proole. Our calculations are chieey concerned with the eeect of eld concentration between (or within) the spiral arms. The possible induction of bisymmetric instead of axisym-metric structured elds is also investigated. We distinguish between models with weak and strong turbulence contribution, that is small and large correlation time corr of interstellar turbulence. For small correlation times we nd axisymmetric steady solutions of even parity showing concentration between the spiral arms. The pitch angles are relatively large and increase with enlarged correlation time. Large correlation times are linked with oscillating BSS type solutions of again even parity, but they are clearly concentrated within the spiral arms.