Be thankful they're in the middle of a sparsely populated area. A coil that large probably blacks out the AM band within a few dozen miles, every amateur radio operator on the wider AM band probably had a noise floor increase or outright blackout within a few hundred miles. And since it's at night, if you knew what you were listening for you could probably have picked it up from 500+ miles.
I understand the fascination with high voltage like this, but it serves no function... It's like fire, there are pyro's that just want to burn things down and make bright lights, and there are artists that want to use to proper application of explosions to perform a needed and useful functions like building destruction and mining, or controlled forest fire burns to prevent the spread of wild fires. Or proper use of high voltages and currents, such as a welder, EDM machining, plating, plasma sputtering and the like.
I know that all sounds a little cheesy, but why is often more important than how, or what. Einstein said as much on several occasions. These toys are cool to watch, but isn't it cooler to do something with that large power, rather than just creating and audio and light show?
I often thing these types of things are overlooked on technical forums, buried in people demanding results and answers to their questions and projects rather than the why of what they're doing.