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We use the Aurora radiation-hydrodynamical simulations to study the mean freepath (MFP) for hydrogen ionizing photons during the epoch of reionization. Wedirectly measure the MFP by averaging the distance 1 Ry photons travel beforereaching an optical depth of unity along random lines-of-sight. Duringreionization the free paths tend to end in neutral gas with densities near thecosmic mean, while after reionizaton the end points tend to be overdense buthighly ionized. Despite the increasing importance of discrete, over-densesystems, the cumulative contribution of systems with $N_{\rm{HI}} \lesssim10^{16.5}~{\rm cm^{-2}}$ suffices to drive the MFP at $z \approx 6$, while atearlier times higher column densities are more important. After reionizationthe typical size of HI systems is close to the local Jeans length, but duringreionization it is much larger. The mean free path for photons originatingclose to galaxies, $\rm{MFP_{gal}}$, is much smaller than the cosmic MFP. Afterreionization this enhancement can remain significant up to starting distancesof $\sim 1$ comoving Mpc. During reionization, however, $\rm{MFP_{gal}}$ fordistances $\sim 10^2 - 10^3$ comoving kpc typically exceeds the cosmic MFP.These findings have important consequences for models that interpret theintergalactic MFP as the distance escaped ionizing photons can travel fromgalaxies before being absorbed and may cause them to under-estimate therequired escape fraction from galaxies, and/or the required emissivity ofionizing photons after reionization.

The mean free path of hydrogen ionizing photons during the epoch of reionization