The Galactic Dynamo

Abstract

In Section V.5 we have shown, at a qualitative level, how differential rotation and helical turbulence together generate the magnetic field. Now we intend to give a more substantiated, detailed picture of the generation process. A reasonable approximation to the galactic dynamo provides the problem of magnetic field growth in a prescribed flow of conductive fluid (the kinematic dynamo). First, this is an unescapable step in the study of the magnetic field origin. Second, the characteristic growth time of the field is only an order of magnitude shorter than the galactic lifetime. Therefore, it should be expected that the generation proceeds currently in the linear or in a weakly non-linear regime which inherits typical properties from the linear stage.