6.5. Hydrodynamical simulations as probes for the structure of the galactic center

Numerical modeling of the interstellar gas in galaxies is an effective approach to infer galactic gravitational structure. This is because the dynamical behavior of gas is very sensitive to the background gravitational potential. Since the dynamical resonances depend closely on the mass distribution and the pattern speed of the non-axisymmetric component, it is possible to determine these dynamical parameters by comparison of numerical simulations and gas observations.

Magnetic Fields in the Disk-Halo Interface

A review is given of large-scale magnetic fields in disks and halos of spiral galaxies. A particular attention is given to vertical field structures, and we discuss their origin and implication on their interaction with halo gas. We point out that the disk-halo magnetic interface plays an important role in circulation of interstellar gas in galaxies, in particular a large-scale circulartion from the galactic center to outer disk regions.

Intermittent Magnetic Fields Generated by Turbulence in Galaxies and Galaxy Clusters

The turbulence of intracluster gas in galaxy clusters and interstellar gas in galaxies can act as a dynamo generating chaotic magnetic fields. These fields are concentrated in ropes with the doubled radius of curvature of about the turbulent correlation length l and thickness where Rm is the magnetic Reynolds number. The field strength within the ropes is close to equipartition with turbulent kinetic energy. These results favorably agree with high—resolution observations of the galaxy cluster around Cyg A and correlation analysis of the Galactic nonthermal background. Ropy magnetic fields in interstellar gas lead to observable variations of, e.g., the Faraday depth at time scale of 1 month.