An electric discharge is the release and transmission of electricity in an applied electric field through a medium such as a gas. Several types of electric discharges occur naturally on Earth (American Geophysical Union, 1986):
Atmospheric lightning, which is thought to be caused by the frictional generation, and separation, of positive and negative charges on ice and dust particles. As the charge on these particles builds up, the result is the often-spectacular discharge of electricity known as lightning. On average, there are 50–100 lightning strikes per second on Earth with most of the activity taking place in equatorial and northern latitudinal regions.
Corona discharges, which are caused by an electrical discharge produced by the ionization of the surrounding atmosphere, generating a luminous plasma (sometime referred to as St. Elmo’s fire, a term used by sailors to describe the glow observed at the top of a ship’s mast during...