Hi Mike, Try Richard Hull. His group did the first modern studies of this phenomena to my knowledge, I remember reading about them in the late Charles Yosts "Electric Spacecraft Journal" Issue #9, 1993. Here's a hint of the article from googling...
http://www.pupman.com/listarchives/1996/march/msg00546.html A careful search of the pupman archives will probably produce as much info as the article, although you'll miss the wonderful pictures and experimental reports from the article. You can probably still get back issues, that one was very good for other articles as well. Charles Yost will be keenly missed. I've not time to reread the article, but from my own experimenting with discharges I've found that certain shapes of electrode tend to have a rectifying effect. Current must be drawn to ground to see the rectification. K.
