The Electric Universe Gallery
Other images:

Description:
The electrons of a lightning are moved by a strong electric field. The unidirectional motion of electrons produces electric currents which attract each other. It does not form a conus (or even a sphere) due to the electrostatic repulsion among electrons. The lightning remains thin and tubular. (Courtesy of A. Hilgenberg D-47533 Kleve).

Source:
Book: "The Electric Universe"