HELICITY GENERATION IN TURBULENT MHD FLOWS

We study turbulent flow of a conducting liquid in a uniform external m agnetic field. It is shown that intense helicity generation is possibl e in the presence of a mean shear flow. It is noted that even though t he mean helicity of the initial flow can be zero, the presence of inte rnal topological structure of the flow, for example the presence of he licity of different signs at different scales, is nevertheless necessa ry for helicity generation. (C) 1998 American Institute of Physics. [S 1063-7761(98)01309-2].