Large-scale Dynamo Action Driven by Velocity Shear and Rotating Convection

By incorporating a large-scale shear flow into turbulent rotating convection, we show that a sufficiently strong shear can promote dynamo action in flows that in the absence of shear do not act as dynamos. Our results are consistent with a dynamo driven by either the shear-current effect or by the interaction between a fluctuating $\alpha$-effect and the velocity shear; they are though inconsistent with either a classical $\alpha^2$ or $\alpha \omega$ mean field dynamo.