Galaxy dynamo in inhomogeneous interstellar medium

Abstract

In some galaxies there are magnetic fields of several microgauss. Their evolution is connected with dynamo mechanism which is based on joint action of alpha-effect and differential rotation. The equations of the dynamo theory usually include some averaged kinematic characteristics of the interstellar turbulence. This approach is quite suitable for galaxies with "calm" interstellar medium. As for the galaxies with intensive star formation or supernovae explosions it will not give proper results. For this case the HII regions are quite small, exist for small-time and their localization can be assumed random. So it is useful to take the dynamo equations with random coefficients, which take one of two values (the first one is connected with HI regions, and the second one - with HII). We have studied the magnetic field evolution in the stochastic dynamo model for some typical cases. From the mathematical point of view, the results show some special effects. Firstly, the magnetic field evolution demonstrates the intermittency effect: higher statistical moments of the field grow faster than the lower ones. Moreover, the magnetic field in this model can have large fluctuations, so we have also described the correlation function of the field.