Minimalist large scale dynamo from shear-driven inhomogeneity

2019/02/13 by F. Ebrahimi, Ebrahimi, F., Eric G. Blackman +1
Biochemistry, Genetics and Molecular Biology · Physics and Astronomy · #FOS: Physical sciences #Fluid Dynamics (physics.flu-dyn) #Geomagnetism and Paleomagnetism Studies #High Energy Astrophysical Phenomena (astro-ph.HE) #Ionosphere and magnetosphere dynamics #Plasma Physics (physics.plasm-ph) #Solar and Space Plasma Dynamics #Solar and Stellar Astrophysics (astro-ph.SR)

paper · pdf · doi:10.48550/arxiv.1902.04737

openalex publication_date 2019/02/13 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28

Abstract

We show that non-axisymmetric, non-helical perturbations in an unstratified shear flow produce a shear-plane averaged electromotive force (EMF) proportional to a spatially dependent kinetic helicity. This new "shear-driven α-effect" can amplify shear-plane averaged magnetic fields, but is undiscoverable when invoking the homogeneity assumption for dynamo coefficients. It is a candidate mechanism underlying large scale field generation in astrophysical, laboratory, and simulated shear flows, and highlights the essentiality of correctly averaging dynamo coefficients and fields.

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