Waves in a two-component model of galactic dynamo: Metastability and stochastic generation

This paper is concerned with the stochastic generation of a large-scale galactic magnetic field and propagation of magnetic fronts in the subcritical regime. Starting with a two-component thin-disk αΩ-dynamo model in the axisymmetric case, we derive the equation for order parameter in the form of a stochastic reaction–diffusion equation with free energy functional. This equation describes subcritical generation of galactic magnetic field as a first-order phase transition in spatially extended system. We consider in particular a situation in which the magnetic field propagates as a plane front. We derive an approximate formula for propagation speed.