| Description: | In the present model for the first time we present results of three-dimensional, fully non-linear MHD simulations of a large-scale magnetic field evolution in a barred galaxy, including the back reaction of magnetic field to gas. We also include the process of cosmic-ray driven dynamo. Additionally we check which physical processes are responsible for magnetic field evolution in tidally influenced spiral galaxies. We solve the MHD equations for gas and magnetic field in a spiral galaxy with gravitationally prescribed bulge, disk and halo which travels along common orbit with the second body. In order to compare our modeling results with observations, we also construct models of high-frequency (Faraday rotation-free) polarized radio emission from the simulated magnetic fields. The model accounts for the effects of projection and limited resolution.
We found that the obtained magnetic field configurations are highly similar to observed maps of the polarized intensity of barred galaxies, because the modeled vectors form coherent structures along the bar and spiral arms. We also found a physical explanation of the problem of inconsistency between the velocity and magnetic fields character present in this type of galaxies. Due to the dynamical influence of the bar the gas forms spiral waves which go radially outward. Each spiral arm forms the magnetic arm which stays much longer in the disk than the gaseous spiral structure. The modeled total energy of magnetic field grows, due to strong compression and shear of non-axisymmetrical bar flows and differential rotation, respectively. However there is no growth of magnetic flux in the plane perpendicular to the axisymmetrical direction. We also obtained polarization maps of tidally influenced spiral galaxies similar to observations. |
