We present the results of simulations of forced turbulence in a slab where
the mean kinetic helicity has a maximum near the mid-plane, generating
gradients of magnetic helicity of both large and small-scale fields. We also
study systems that have poorly conducting buffer zones away from the midplane
in order to assess the effects of boundaries. The dynamical alpha quenching
phenomenology requires that the magnetic helicity in the small-scale fields
approaches a nearly static, gauge independent state. To stress-test this steady
state condition we choose a system with a uniform sign of kinetic helicity, so
that the total magnetic helicity can reach a steady state value only through
fluxes through the boundary, which are themselves suppressed by the velocity
boundary conditions. Even with such a set up, the small-scale magnetic helicity
is found to reach a steady state. In agreement with earlier work, the magnetic
helicity fluxes of small-scale fields are found to be turbulently diffusive. By
comparing results with and without halos, we show that artificial constraints
on magnetic helicity at the boundary do not have a significant impact on the
evolution of the magnetic helicity, except that "softer" (halo) boundary
conditions give a lower energy of the saturated mean magnetic field.Comment: 12 pages, 5 figures, submitted to GAF