  Magnetic helicity fluxes are investigated in a family of gauges in which the
contribution from ideal magnetohydrodynamics takes the form of a purely
advective flux. Numerical simulations of magnetohydrodynamic turbulence in this
advective gauge family exhibit instabilities triggered by the build-up of
unphysical irrotational contributions to the magnetic vector potential. As a
remedy, the vector potential is evolved in a numerically well behaved gauge,
from which the advective vector potential is obtained by a gauge
transformation. In the kinematic regime, the magnetic helicity density evolves
similarly to a passive scalar when resistivity is small and turbulent mixing is
mild, i.e. when the fluid Reynolds number is not too large. In the dynamical
regime, resistive contributions to the magnetic helicity flux in the advective
gauge are found to be significant owing to the development of small length
scales in the irrotational part of the magnetic vector potential.
