Sharp magnetic structures from dynamos with density stratification
arXiv:1607.08897 · doi:10.1093/mnras/stx148
Abstract
Recent direct numerical simulations (DNS) of large-scale turbulent dynamos in strongly stratified layers have resulted in surprisingly sharp bipolar structures at the surface. Here we present new DNS of helically and non-helically forced turbulence with and without rotation and compare with corresponding mean-field simulations (MFS) to show that these structures are a generic outcome of a broader class of dynamos in density-stratified layers. The MFS agree qualitatively with the DNS, but the period of oscillations tends to be longer in the DNS. In both DNS and MFS, the sharp structures are produced by converging flows at the surface and might be driven in nonlinear stage of evolution by the Lorentz force associated with the large-scale dynamo-driven magnetic field if the dynamo number is at least 2.5 times supercritical.
13 pages, 25 figures, 3 tables
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Cited by in corpus (4)
- Advances in mean-field dynamo theory and applications to astrophysical turbulence
- Magnetic concentrations in stratified turbulence: the negative effective magnetic pressure instability
- Stellar Dynamos with Solar and Anti-solar Differential Rotations: Implications to Magnetic Cycles of Slowly Rotating Stars
- Analytic solution of an oscillatory migratory alpha^2 stellar dynamo