how can you make free electrons in the ionosphere collide?

Answer 1

You really can't. There are very few free electrons in the ionosphere. Typically, free electrons are discharged by plasma.
Electrons are not really considered to be in any specific location. They exist, for all purposes, are a nascent cloud. Electrons are only percentages of the probability of an electron being there.
Since electrons repel each other, as they get closer, the repulsion increases. And since an electron doesn't exist at any singular point in space, you can't really get electrons to collide.