Huge Dynamo action in spiral galaxies

Conférence de Luke Chamandy, Inter-University Center for Astronomy and Astrophysics

Résumé

Large-scale magnetic fields in disk galaxies, visible in polarized synchrotron emission and its Faraday rotation, require a generation mechanism that orders magnetic fields on scales larger than the turbulent scale; what is referred to as a mean-field dynamo. In many cases, these fields exhibit deviations from axial symmetry, in particular where the large-scale field is enhanced in ‘spiral magnetic arms’ akin to, but sometimes phase-shifted from, the optical spiral arms.

We present mean-field galactic dynamo models which include non-linear effects arising from magnetic helicity balance (the dynamical alpha-quenching), the delayed response of the mean electromotive force to variations of the mean magnetic field and turbulence parameters (the temporal non-locality), galactic outflows, and realistic spiral structure and evolution. In particular, we isolate three important physical effects which apparently contribute to the formation of magnetic arms.

Présentée par le Groupe Astronomie et astrophysique du Département de physique de l'Université de Montréal. Cette conférence est destinée à des spécialistes dans le domaine de l'astrophysique et sera donnée en anglais.