Oral Presentation

Vorticity, helicity and mean flows in supernova-driven turbulence

Author(s): Maarit Käpylä (Max Planck Institute for Solar System Research, Aalto University) Frederick Gent (ReSoLVE Centre of Excellence, Aalto University) Miikka Väisälä (ASIAA, University of Helsinki, Aalto University) Graeme Sarson (Newcastle University)

Presenter: Miikka Väisälä (Academia Sinica, Institute of Astronomy and Astrophysics)

We performed hydrodynamical simulations of supernova-driven turbulence in a local stratified kiloparsec-scale shearing box frame to examine the generation of turbulent flows. We included full thermodynamics in our models with parametrized heating and cooling terms. We ran our simulations with different shear/rotation rates and also used shear and rotation rates with opposite signs to separate their contributions. We found that with thermal SN-turbulence vorticity dominates over compressive flows. This is possible due to the baroclinicity of the flow, especially at the hot clusters of supernova bubbles. We measured generation of net helicity, especially withing the hot gas phase, although with near solar system rotation and shear rates the values of net helicity approached near cancellation. We also discovered that SN-turbulence can generate periodical mean flows in differentially rotating frame. The phenomenon was recognized as the anisotropic kinetic alpha (AKA) effect and this was the first time the AKA-effect has been observed emerging in direct numerical simulations without intentionally inducing it.