Magnetic Fields and Rotation of Spiral Galaxies

We present a simplified model in which we suggest that two important galactic problems- the magnetic field configuration at large scales and the flat rotation curve-may be simultaneously explained. A highly convective disc produces a high turbulent magnetic diffusion in the vertical direction, establishing a merging of extragalactic and galactic magnetic fields. The outer disc may then acquire a magnetic energy gradient very close to the gradient required to explain the rotation curve, without the hypotheses of galactic dark matter. Our model predicts symmetries of the galactic field in noticeable agreement with the large scale structure of our Galaxy. (Author) 46 refs