2014/09/30 by F. Vazza, M. Brüggen, C. Gheller +1 · 2 citations
Physics and Astronomy · #Astrophysics #Astrophysics and Star Formation Studies #Dynamo #Galaxies: Formation, Evolution, Phenomena #Galaxy #Galaxy cluster #Intergalactic travel #Intracluster medium #Magnetic field #Physics #Quantum mechanics #Redshift #Solar and Space Plasma Dynamics #Structure formation #astro-ph.CO
paper · pdf · doi:10.1093/mnras/stu1896
MNRAS accepted, in press. 18 pages, 18 Figures. New version to match with the one published in MNRAS. Updated publication list and footnote added to the title as obituary notice
arxiv created 2014/10/23 · openalex publication_date 2014/10/29 · arxiv updated 2015/06/22 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
The amplification of primordial magnetic fields via a small-scale turbulent dynamo during structure formation might be able to explain the observed magnetic fields in galaxy clusters. The magnetization of more tenuous large-scale structures such as cosmic filaments is more uncertain, as it is challenging for numerical simulations to achieve the required dynamical range. In this work, we present magnetohydrodynamical cosmological simulations on large uniform grids to study the amplification of primordial seed fields in the intracluster medium (ICM) and in the warm–hot-intergalactic medium (WHIM). In the ICM, we confirm that turbulence caused by structure formation can produce a significant dynamo amplification, even if the amplification is smaller than what is reported in other papers. In the WHIM inside filaments, we do not observe significant dynamo amplification, even though we achieve Reynolds numbers of Re ∼ 200–300. The maximal amplification for large filaments is of the order of ∼100 for the magnetic energy, corresponding to a typical field of a few ∼nG starting from a primordial weak field of 10−10 G (comoving). In order to start a small-scale dynamo, we found that a minimum of ∼102 resolution elements across the virial radius of galaxy clusters was necessary. In filaments we could not find a minimum resolution to set off a dynamo. This stems from the inefficiency of supersonic motions in the WHIM in triggering solenoidal modes and small-scale twisting of magnetic field structures. Magnetic fields this small will make it hard to detect filaments in radio observations.