FLOW HELICITY IN A SIMPLIFIED STATISTICAL-MODEL OF A FAST DYNAMO

The role of kinetic helicity in small-scale fast dynamo action is inve stigated by employing a simple statistical model for the underlying fl ow with statistics that are Gaussian distributed, temporally delta-cor related and spatially homogeneous and isotropic. In order to focus on small-scale dynamo action we restrict our attention to flows possessin g no net kinetic helicity. With the help of a diagrammatic technique a nd a numerical calculation we show that the dynamo growth rate is inde pendent of the kinetic helicity as the magnetic Reynolds number R-m -- > infinity. It is indicated that the latter enhances the growth of the magnetic energy only for finite R-m. (C) 1997 Elsevier Science B.V.