A model for the bilateral interaction between dynamo action and star formation in galactic discs.

A minimum comprehensive model is constructed for the interaction between the large-scale star formation (SF) and the large-scale magnetic field in disk galaxies. Numerical integrations of the model evolution equations show that there are only small regions of simultaneous occurrence of star formation and dynamo action in the parameter space defined by the initial surface density of the gaseous disk and the initial effective sound velocity of the gas. The reason for this is that SF needs a large surface density and/or a small sound velocity but these conditions lead to a thin disk which opposes dynamo action. If the energy released from SF is of the order of the gas energy density from where stars were formed, it is not enough to increase the disk thickness sufficiently, and hence SF seems unable to activate a dynamo. In contrast, the magnetic field developed through dynamo action can make the SF rate significantly large.