  Using simulations of helically driven turbulence, it is shown that the ratio
of kinetic to magnetic energy dissipation scales with the magnetic Prandtl
number in power law fashion with an exponent of approximately 0.6. Over six
orders of magnitude in the magnetic Prandtl number the magnetic field is found
to be sustained by large-scale dynamo action of alpha-squared type. This work
extends a similar finding for small magnetic Prandtl numbers to the regime of
large magnetic Prandtl numbers. At large magnetic Prandtl numbers, most of the
energy is dissipated viscously, lowering thus the amount of magnetic energy
dissipation, which means that simulations can be performed at magnetic Reynolds
numbers that are large compared to the usual limits imposed by a given
resolution. This is analogous to an earlier finding that at small magnetic
Prandtl numbers, most of the energy is dissipated resistively, lowering the
amount of kinetic energy dissipation, so simulations can then be performed at
much larger fluid Reynolds numbers than otherwise. The decrease in magnetic
energy dissipation at large magnetic Prandtl numbers is discussed in the
context of underluminous accretion found in some quasars.
