Average cross-coherence of all image-cube pairs. The top row shows cross-coherence of transient RFI in Stokes I images in the presence of thermal noise with different levels (left to right columns: t_obs = 1 min, 4.17 h, 25 h), and the bottom row shows the cross-coherence of the corresponding thermal noise levels. The transient RFI coherence in the presence of thermal noise is visually indiscernible from the noise coherence itself.