Artificial? Obviously. Still it is interesting to think of how such things could arise in nature. Spontaneous organization of molecules and biological systems give an amazing diversity of behavior.
Which file are your images from? I've downloaded the first galnpole (Galactic North Pole?) file and there are a lot of modulated signals in there but I can't find the ones in your image.
Is it just me or does anyone else think those waterfall plots look a lot like screenshots from the classic Space Invaders video game?
[no-glossary] http://220.127.116.11/download/2010-10-22-galnpole-1543_2/ files 01, 02, and 03 [/no-glossary]