3D numerical global simulations of cosmic ray driven dynamo in barred and dwarf irregular galaxies

In this paper we present our results of three-dimensional global numerical simulations of barred and irregular galaxies including a process of a cosmic-ray driven dynamo in respect to star formation rates. We are looking for the answer which physical mechanism could be liable for magnetic field evolution observed in both types of the mentioned galaxies. Our main goal is to compare our numerical results with observations, so we prepare model of high-frequency (Faraday rotation-free) polarized radio emission maps from the resulted magnetic fields and cosmic rays (CR) both active in our modeled galaxies. The main result is that CR driven dynamo can amplify weak magnetic fields up to several mG within few Gyr in barred galaxies. Magnetic field structures in model of the barred galaxies are alike the observed in maps of the polarized intensity in these galaxies. Our results also provide new information about the observed polarimetry properties of barred and spiral galaxies: the quadrupole modes of modeled galaxies often present in real barred galaxies, a stochastic nature of magnetic field reversals (present in the Milky Way), the dipole modes of magnetic structures resulted at certain stages of the galactic evolution (e.g. NGC 4631). In the case of dwarf irregular galaxies despite the adverse conditions (low mass, slow rotation) the dynamo can operate. Observations and numerics show some indication for some dynamo thresholds — needs further deep investigation. SFR/SNR is the key parameter, but to high destroys the rotation: but we need both to operate the large scale dynamo. Possible magnetization of the IGM.