  We perform a suite of two- and three-dimensional magnetohydrodynamic (MHD)
simulations with the Athena code of the non-driven Kelvin-Helmholtz instability
in the subsonic, weak magnetic field limit. Focusing the analysis on the
non-linear turbulent regime, we quantify energy transfer on a scale-by-scale
basis and identify the physical mechanisms responsible for energy exchange by
developing the diagnostic known as spectral energy transfer function analysis.
At late times when the fluid is in a state of MHD turbulence, magnetic tension
mediates the dominant mode of energy injection into the magnetic reservoir,
whereby turbulent fluid motions twist and stretch the magnetic field lines.
This generated magnetic energy turbulently cascades to smaller scales, while
being exchanged backwards and forwards with the kinetic energy reservoir, until
finally being dissipated. Incorporating explicit dissipation pushes the
dissipation scale to larger scales than if the dissipation were entirely
numerical. For scales larger than the dissipation scale, we show that the
physics of energy transfer in decaying MHD turbulence is robust to numerical
effects.
