Modeling spatio temporal nonlocality in mean field dynamos
2012 (English)In: Astronomical Notes - Astronomische Nachrichten, ISSN 0004-6337, E-ISSN 1521-3994, Vol. 333, no 1, 71-77 p.Article in journal (Refereed) Published
When scale separation in space or time is poor, the mean-field alpha effect and turbulent diffusivity have to be replaced by integral kernels by which the dependence of the mean electromotive force on the mean magnetic field becomes nonlocal. Earlier work in computing these kernels using the test-field method is now generalized to the case in which both spatial and temporal scale separations are poor. The approximate form of the kernel for isotropic stationary turbulence is such that it can be treated in a straightforward manner by solving a partial differential equation for the mean electromotive force. The resulting mean-field equations are solved for oscillatory alpha-shear dynamos as well as alpha(2) dynamos with alpha linearly depending on position, which makes this dynamo oscillatory, too. In both cases, the critical values of the dynamo number is lowered due to spatio-temporal nonlocality.
Place, publisher, year, edition, pages
2012. Vol. 333, no 1, 71-77 p.
magnetic fields, magnetohydrodynamics (MHD), methods: numerical
Astronomy, Astrophysics and Cosmology
IdentifiersURN: urn:nbn:se:su:diva-79707DOI: 10.1002/asna.201111625ISI: 000303312400010OAI: oai:DiVA.org:su-79707DiVA: diva2:552531