When I see TT Browns work I am reminded of this figure 4 on page 170 in Maxwell's paper:
On Physical Lines of Force (note that the paper starts on page 161)
Maxwell's work did not depend on ions and ultimately led physicists the world over to conclude that EM radiation would propagate freely through a vacuum thus dispensing with the notion that a medium was necessary. And of course the
Michelson Morely Experiment was intended to end the debate.
However, Nikola Tesla raised a very interesting hypothesis by stating that the Aether would be and is dragged along with the Earth as it rotates. In this case the Michelson Morely experiment would fail even when an Aether was present. It is very interesting that recent tests such as
Gravity Probe-B and
The Earth Drags Space and Time - NASA show that Space-Time is dragged along with the Earth similar to what Tesla indicated.
I have come to believe that what the scientific community now refers to as Space-Time is the same stuff that Tesla called the Aether.
If so, then the force we see in a narrowing field, whether Electrical or Magnetic, should exist anywhere Space-Time exists regardless of vacuum or high pressure gasses.
As regards the Earths charge see
How Does The Earth Benefit From Lightening six questions down.
As regards Steven Mark's TPU - one thing I find interesting is the gyroscopic effect that it exhibited. While Einstein's Mass Energy equivalence is broadly accepted I have always had a reservation regarding the interplay between gravity and energy. I have always viewed massless energy to be unaffected by gravity because it coexists with Space-Time in a non-displacement manner. Since inertia and thereby gyroscopic effects are a form of artificial gravity I am inclined to believe that Mark's TPU is moving mass, aka electrons or some other particle around the loop. Unless of course the effect is only something else that mimics gyroscopic activity.

In looking at his setup, especially the exposed videos where the wiring can be seen, I am inclined to think that he has a round robin configuration where the final stage is re-entry in phase with the first stage. So all that is needed is a small battery or magnetic pulse to get the system into resonance. If that resonance is sympathetic to any of a multitude of power sources, man made or natural, then the oscillation would continue and any excess energy could be extracted. It would be nice to see if the external source could be identified. Whatever it is, it must be operating at some harmonic of Steven's frequency of operation. I've read about the imploding TV sets etc. and having a deep background in that technology I cannot discount his claims. I can't help but wonder if there was a Piezo effect in play as many of the older tubes had a high concentration of Quartz in their makeup. Nevertheless Steven eventually moved to Solid State AFAIK so that wouldn't explain his source.
Look for commonality between Moray, Tesla, Marks & Schwartz. That commonality will no doubt point to the source. Each device is different, but each device has something in common with all the others.