We explore the geometry and dynamics of cosmological ionization fronts using CROC simulations, and demonstrate that their statistical properties are well described by an analytic barrier-crossing model applied to the initial Gaussian density field in overdense regions.

We model cosmic-ray mediated thermal fronts in the CGM and show how CR heating, conduction, and cooling combine to set their structure and line diagnostics.

We study the physical origin of Lyα transmission spikes during reionization using CROC simulations. We show that these rare high-transmission features arise primarily from low-density regions and are governed by the large-scale ionizing background rather than enhanced flux from nearby galaxies.