The Generation of Magnetic Fields in Astrophysical Bodies. II. The Galactic Field

The gaseous disk of the Galaxy is subject to nonuniform rotation and internal turbulence. The rotation causes the turbulence to be cyclonic. Formal solution of the dynamo equations in a slab of gas, representing the galactic disk, produces regenerative modes, in which the aximutal field is an even function of the distance a from the central plane of the slab. Inclusion of the ` eddy diffusivity" of the turbulence in the dissipation terms of the dynamo equations gives growth times of 108 years. Hence we suggest that the magnetic field of the Galaxy is generated by the combination of nonuniform rotation and turbulence in the gaseous disk. The dynamo principle responsible for the magnetic field of Earth and of tlie Sun appears to be operative on a galactic scale, too.