I was reading Michael Collins' account of the Apollo 11 TLI burn , and I wonder wheter the "flashes", "lightning", "sparks flying" and "insistent fireflies" he and Neil Armstrong saw out of the Command module windows could be due to the engine somehow creating a high voltage during operation.
The phenomenon lasted just for the duration of the burn, so it is clearly different from the transient white flashes that some astronauts have seen when a charged particle impacts their brain in space. And it cannot be due to ice fragments or gas particles floating around the ship, as these would go away fast as soon as the engine starts moving the ship.
The burn was performed by the Saturn IV-B cryogenic engine (H2 + O2). I guess a pure combustion shouldn't produce high voltage, but maybe little metal particles flying off the turbopumps could create friction against the engine's metallic nozzle? Collins' description points to an electrical phenomenon, something like Saint Elmo's fire but in space. I'm thinking about the engine accidentally becoming a Van de Graaff generator, which in conjunction with some external phenomenon (solar wind, Van Allen belts) could have resulted in the sparks. So my question is:
TL;DR: Can vacuum rocket engines produce high voltages during operation?
Side questions (not important, but still interesting):
- Was there ever an official explanation for the flashes?
- Has any other space flight ever reported something similar?
- If it was indeed high voltage, shouldn't astronauts wear electrician-grade insulated globes for just in case the voltage mades its way into some switches or part of the cabin?
 Collins, M. (2019) Carrying the fire: An Astronaut's journeys. 50th anniversary edition. New York: Farrar, Straus and Giroux. p 372. ISBN 978-0-374-53776-0