We have recalculated the diffusion expected from the quasi-linear theory of the lower hybrid drift instability at the Earth's magnetopause. The resulting diffusion coefficient is marginally large enough to explain the thickness of the boundary layer under quiet conditions, based on observational upper limts for the wave intensities. Thus one possible model for the boundary layer could involve equilibrium between the diffusion arising from lower hybrid waves and various loss processes. ¿American Geophysical Union 1991