Some flavor AGM-88. HARM or AARGM, not sure which from the photo. Standard fare for the G bubbas.
99% sure it’s an AARGM, they look like they have the ceramic radome, plus there’s no utility in a Growler carrying a HARM CATM as everything HARM related can be simulated in the jet (unless carrying the HARM CATM to check the T&R box is still a thing).
Another reason to carry it back is that the CATMs are a wing pooled asset, so it can be handed off sooner to another squadron that needs it.
I officially feel old now because my JO buddy is the skipper of that squadron.