Well, the arcing of light actually 
I was running a train tonight and saw what I thought was lights on my newly painted GP9 flickering.
I watched again as the train passed, only to see a huge blue ball shoot from underneath a tank car that was directly behind the engine. I immediately put the train in emergency stop and pulled the tank car for service.
What I found were pit marks on one of the wheels and marks on the track where the incident occurred repeatedly.
The truck the wheel was in seemed tighter than the other so I pulled the frame and removed the truck, but couldn't see anything that might have been a problem. When I put the car back together I made sure the truck was not screwed down as much as before.
I also found a slight misalignment in the track, just before the pitting. It is located at the end of my drop-down section where I access the room. I figure I must have bumped into it at some point and didn't notice it until now. None of the other cars were doing it though, so it must have been the combination of the 2 problems.
Problem solved, but not before it pitted the wheel/track and actually shutdown the layout twice.
I'm going to make sure I inspect the track for alignment issues next time I clean it, don't want another light show 
I would imagine that was like catching a bowling ball in mid-air 
