Supernova-driven turbulence and magnetic field amplification in disk galaxies [Elektronische Ressource] / Oliver Gressel

Astrophysikalisches Institut PotsdamMagnetohydrodynamikSupernova-driven Turbulence andMagnetic Field Amplificationin Disk GalaxiesOliver Gressel Published online at the Institutional Repository of the University of Potsdam: http://opus.kobv.de/ubp/volltexte/2009/2909/ urn:nbn:de:kobv:517-opus-29094 [http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-29094] Abstract: Supernovae are known to be the dominant energy source for driv-ing turbulence in the interstellar medium. Yet, their effect on magnetic fieldamplification in spiral galaxies is still poorly understood. Analytical modelsbased on the uncorrelated-ensemble approach predicted that any created fieldwill be expelled from the disk before a significant amplification can occur. Bymeans of direct simulations of supernova-driven turbulence, we demonstratethat this is not the case. Accounting for vertical stratification and galacticdifferential rotation, we find an exponential amplification of the mean field ontimescales of 100Myr. The self-consistent numerical verification of such a “fastdynamo” is highly beneficial in explaining the observed strong magnetic fieldsinyounggalaxies. We, furthermore, highlighttheimportanceofrotationinthegeneration of helicity by showing that a similar mechanism based on Cartesianshear does not lead to a sustained amplification of the mean magnetic field.