Fluctuation dynamo amplified by intermittent shear bursts in convectively driven magnetohydrodynamic turbulence

¹ Max-Planck-Institut für Plasmaphysik, 85748 Garching, Germany
e-mail: Jane.Pratt@ipp.mpg.de
² Max-Planck-Institut für Sonnensystemforschung, 37191 Katlenburg-Lindau, Germany
³ Faculty of Engineering and the Environment, University of Southampton, UK
⁴ Center for Astronomy and Astrophysics, ER 3-2, TU Berlin, Hardenbergstr. 36, 10623 Berlin, Germany

Received: 31 March 2013
Accepted: 26 July 2013

Abstract

Intermittent large-scale high-shear flows are found to occur frequently and spontaneously in direct numerical simulations of statistically stationary turbulent Boussinesq magnetohydrodynamic (MHD) convection. The energetic steady state of the system is sustained by convective driving of the velocity field and small-scale dynamo action. The intermittent emergence of flow structures with strong velocity and magnetic shearing generates magnetic energy at an elevated rate on time scales that are longer than the characteristic time of the large-scale convective motion. The resilience of magnetic energy amplification suggests that intermittent shear bursts are a significant driver of dynamo action in turbulent magnetoconvection.