A plasma channel can be formed in the following ways.
A plasma channel has a low electrical resistance and, once formed, will permit continuous current flow if the energy source that heats the plasma can be maintained.
Unlike a normal electrical conductor, the resistance (and voltage drop) across an unconfined plasma channel decreases with increasing current flow, a property called negative resistance.
As a result, an electric spark that initially required a very high voltage to initiate avalanche breakdown within the insulating gas will rapidly evolve into a hot, low-voltage electric arc if the electrical power source can continue to deliver sufficient power to the arc.
On Earth, plasma channels are most frequently encountered in lightning storms.