I realize the idea is highly unlikely, and I am by no means in the interest to build such a device, but more on the side to make an interesting paper. That being said in response to davven. There should be on average a steady state magnetic field, such that there is a way to direct the protons and electrons. Once electrons have been been boiled off in an electron gun, they shouldn't experience much "friction" so it shouldn't matter the distance it travels. The hardest part would be to create a steady stream, and perhaps for this reason, the stream might only work for short distances.
In response to zapperz. Most internet article describe ionized gas in space as a plasma. Hence when I refer to the electron and proton streams, they fall under the same category. And, like I said I know it would be very difficult to build such a connection between two streams, but if they did connect, would it have the same effect as lightning, such that a current would flow. I know that it wouldn't have the casdade effect, but I think it may be possible to extract energy from two charges in space.