Strong large scale magnetic fields in rotating convection-driven dynamos: the important role of magnetic diffusion

Abstract

Natural dynamos such as planets and stars generate global scale magnetic field despite the inferred presence of small scale turbulence. Such systems are known as large scale dynamos and are typically driven by convection and influenced by rotation. Previous numerical studies of rotating dynamos generally find that the large scale magnetic field becomes weaker as the flow becomes more turbulent. The underlying physical processes necessary for sustaining so-called large scale dynamos is therefore still debated. Here we use a suite of numerical simulations to show that strong large scale magnetic fields can be generated in rotating convective turbulence provided that two conditions are satisfied: (1) the flow remains rotationally constrained; and (2) magnetic diffusion is important on the small convective length scale. These findings are in agreement with previous asymptotic predictions and suggest that natural dynamos might satisfy these two conditions.

6 pages, 4 figures

References in corpus (4)

• Generation of magnetic fields by large-scale vortices in rotating convection
• Convection-driven kinematic dynamos at low Rossby and magnetic Prandtl numbers
• The Breakdown of the Anelastic Approximation in Rotating Compressible Convection: Implications for Astrophysical Systems
• Large-scale-vortex dynamos in planar rotating convection

Cited by in corpus (3)

• Asymptotic behaviour of rotating convection-driven dynamos in the plane layer geometry
• Detectability of axisymmetric magnetic fields from the core to the surface of oscillating post-main sequence stars
• Effects of kinematic and magnetic boundary conditions on the dynamics of convection-driven plane layer dynamos