Global enhancement and structure formation of the magnetic field in spiral galaxies
arXiv:1710.04307 · doi:10.1051/0004-6361/201629988
Abstract
We study numerically large-scale magnetic field evolution and its enhancement in gaseous disks of spiral galaxies. We consider a set of models with the various spiral pattern parameters and the initial magnetic field strength with taking into account gas self-gravity and cooling/heating. In agreement with previous studies, we find out that galactic magnetic field is mostly aligned with gaseous structures, however small-scale gaseous structures (spurs and clumps) are more chaotic than the magnetic field structure. In spiral arms magnetic field strongly coexists with the gas distribution, in the inter-arm region we see filamentary magnetic field structure. Simulations reveal the presence of the small-scale irregularities of the magnetic field as well as the reversal of magnetic field at the outer edge of the large-scale spurs. We provide evidences that the magnetic field in the spiral arms has a stronger mean-field component, and there is a clear inverse correlation between gas density and plasma-beta parameter, compared to the rest of the disk with a more turbulent component of the field and an absence of correlation between gas density and plasma-beta. We show the mean field growth up to 3-10 in the cold gas during several rotation periods (500-800 Myr), whereas ratio between azimuthal and radial field is equal to 4/1. Mean field strength increases by a factor of 1.5-2.5 for models with various spiral pattern parameters. Random magnetic field component can reach up to 25 % from the total strength. By making an analysis of the time-depended evolution of radial Poynting flux we point out that the magnetic field strength is enhanced stronger at the galactic outskirts which is due to the radial transfer of magnetic energy by the spiral arms pushing the magnetic field outward. Our results also support the presence of sufficient conditions for development of MRI at distances >11 kpc.
15 pages, 15 figures, accepted for publication in A&A
References in corpus (24)
- Strong magnetic fields in normal galaxies at high redshifts
- A new Jeans resolution criterion for (M)HD simulations of self-gravitating gas: Application to magnetic field amplification by gravity-driven turbulence
- Star Formation in Disk Galaxies. I. Formation and Evolution of Giant Molecular Clouds via Gravitational Instability and Cloud Collisions
- CO-dark gas and molecular filaments in Milky Way type galaxies
- Direct simulations of a supernova-driven galactic dynamo
- Evolution of magnetic fields in galaxies and future observational tests with the Square Kilometre Array
- Magnetohydrodynamic Simulations of Disk Galaxy Formation: the Magnetization of The Cold and Warm Medium
- Formation of Spiral-Arm Spurs and Bound Clouds in Vertically Stratified Galactic Gas Disks
- Global galactic dynamo driven by cosmic-rays and exploding magnetized stars
- The formation of molecular clouds in spiral galaxies
- Spurs and feathering in spiral galaxies
- The ISM in spiral galaxies: can cooling in spiral shocks produce molecular clouds?
- The supernova-regulated ISM. II. The mean magnetic field
- Instabilities of Spiral Shocks -- II. A quasi-steady State in the multi-phase inhomogeneous ISM
- Nature of the Wiggle Instability of Galactic Spiral Shocks
- Magnetic fields and the dynamics of spiral galaxies
- Dynamo coefficients from local simulations of the turbulent ISM
- Magnetic Spiral Arms and Galactic Outflows
- Numerical code for multi-component galaxies: from N-body to chemistry and magnetic fields
- The magnetic field structure of the central region in M31
- Magnetic field evolution and reversals in spiral galaxies
- Periodicity makes galactic shocks unstable - I. Linear analysis
- The formation of regular interarm magnetic fields in spiral galaxies
- Do magnetic fields influence gas rotation in galaxies?