The lightning is often a discharge in advance. The (negative) charge slide occasionally a little further on in the conductive channel, wherein said channel is highlighted each time something. The lowering speed of the discharge is "only" about 1,500 kilometers per second.
The main discharge provides the lightning that we usually perceive (which appears from the clouds to the earth, but not in reality). After the discharge of this strong flow fills the entire channel. This is called the main discharge or sometimes the 'backlash' (return stroke).
This phenomenon, with intense light accompanied, moves at about 100,000 to 150,000 km / s from the earth to the cloud. In this situation, the electrons move down and our speech becomes the current direction counted up. After all, the electric current runs from plus to minus, as opposed to the electrons.
But the question now is how electrons that emerge give a flash of light which goes up?