Turbulence simulation of fratricide alpha-Omega dynamos

by Alexander Hubbard (Nordita)

Wednesday 2 Feb 2011, 13:30 → 14:30 Europe/Stockholm

122:026

Helically forced magneto-hydrodynamic shearing-sheets can support different large-scale dynamo modes, although the α-Ω mode is generally expected to dominate as it is the fastest growing. In an α-Ω dynamo, most of the field amplification is produced by shear. Differential rotation is a ubiquitous source of shear in astrophysics so astrophysical large-scale magnetic fields are believed to usually be the result of such dynamos. We present shearing-sheet simulations where the α-Ω mode is instead replaced, after initial dominance and saturation, by an orthogonal α mode, which is sustained by the helical turbulence alone. We show that there are at least two processes by which this transition can occur.

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