High Omega Gain in High Shear Dynamo Flow with Low Turbulence

The omega-phase of the liquid sodium alpha-omega dynamo experiment at NMIMT in cooperation with LANL has demonstrated a high toroidal field B$_\phi$ that is 8 times B$_r$ where B$_r$ is the radial component of an applied poloidal magnetic field. This enhanced toroidal field is produced by the rotational shear in stable Couette flow within liquid sodium at high Re $\sim $ 1.4 x 10$^{7}$ and magnetic Reynolds number Rm $\sim $ 120. A small turbulence in stable Taylor-Couette flow is caused by Ekman flow at the end walls, which causes an estimated turbulence energy fraction of (delta v/v)$^2$ $\sim $ 10$^{-3}$. This result compared to three highly turbulent flow measurements with an omega gain of $\sim $1.4 is interpreted as ``turbulence results primarily in the diffusion and dissipation of magnetic flux as compared to the possible creation of magnetic flux by dynamo action''. Large scale low turbulence, coherent flows as opposed to turbulent flows alone are then required to create the magnetic fields of the universe.