Mystery Signal on 8992 kHz USB

Today while monitoring USAF HFGCS on 8992 kHz USB I started hearing the signal in the YouTube video below. Not much to add to what's in the video other than I've heard it before and decided to record it. The first minute or two should suffice, unless you know or hear something something I don't. It seems repetitious to me.

My best guess is that this is an OTHR. Sounds similar to samples here: http://www.sigidwiki.com/wiki/PLUTO_II_OTH_Radar