John, those are absolutely fascinating!I wasn't really sure whether the effect you saw on USC a couple weeks back was a propagation anomaly or not, because the multiple extra traces were symmetrical about both sides of the original signal and were spaced at constant multiples of 2 Hz. That's somewhat like intermod I've noticed on HiFER traces when CODAR is at just the right (wrong) levels. But there is no doubt in my mind that these are signs of some really wild propagation!
There's bifurcation, multifurcation (?!), and I don't know what all! Especially intriguing, to me, is the right hand side of the NC square wave. In that one, it's the strongest reflection that's undergoing quasi-sinusoidal frequency shifts...and mostly on the upper shift frequency, but at least once on the lower. The weaker trace a Hz or so below the bright one is flat on both the high and low state.
I wish we had some way to visualize what was going on up there at the time. I sort of picture a plasma equivalent of mammatus clouds being pushed around, but who can tell? I wonder if anything showed up on the satellite that monitors airglow.
John