The dependence of the dynamo alpha on vorticity

We use data from numerical simulations of dynamo-generated turbulence in the shearing box approximation to determine the dynamo alpha-effect and its dependence on the rotation law Omega(r). The data suggest that the dynamo alpha is not simply proportional to the local angular velocity Omega(r), as is usually assumed, but rather is proportional to the local vorticity omega(r)=r^-1d/dr(Omegar^2). We also find tentative evidence to support the proposition that the backreaction of the magnetic field on alpha sets in when the field reaches equipartition with the energy in the turbulent motions. Furthermore, we propose an explanation as to why the sign of alpha is found to be opposite to that in the standard picture.