Vorticity production through rotation, shear, and baroclinicity
2011 (English)In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 528, A145- p.Article in journal (Refereed) Published
Context. In the absence of rotation and shear, and under the assumption of constant temperature or specific entropy, purely potential forcing by localized expansion waves is known to produce irrotational flows that have no vorticity. Aims. Here we study the production of vorticity under idealized conditions when there is rotation, shear, or baroclinicity, to address the problem of vorticity generation in the interstellar medium in a systematic fashion. Methods. We use three-dimensional periodic box numerical simulations to investigate the various effects in isolation. Results. We find that for slow rotation, vorticity production in an isothermal gas is small in the sense that the ratio of the root-mean-square values of vorticity and velocity is small compared with the wavenumber of the energy-carrying motions. For Coriolis numbers above a certain level, vorticity production saturates at a value where the aforementioned ratio becomes comparable with the wavenumber of the energy-carrying motions. Shear also raises the vorticity production, but no saturation is found. When the assumption of isothermality is dropped, there is significant vorticity production by the baroclinic term once the turbulence becomes supersonic. In galaxies, shear and rotation are estimated to be insufficient to produce significant amounts of vorticity, leaving therefore only the baroclinic term as the most favorable candidate. We also demonstrate vorticity production visually as a result of colliding shock fronts.
Place, publisher, year, edition, pages
2011. Vol. 528, A145- p.
turbulence, dynamo, magnetohydrodynamics (MHD), ISM: bubbles, galaxies: magnetic fields, galaxies: ISM
Physical Sciences Astronomy, Astrophysics and Cosmology
IdentifiersURN: urn:nbn:se:su:diva-69076DOI: 10.1051/0004-6361/201015661ISI: 000288541600092OAI: oai:DiVA.org:su-69076DiVA: diva2:475390
authorCount :22012-01-102012-01-102012-10-15Bibliographically approved