It is known that the breakdown mechanism of [SF.sub.6] is streamer and stepped leader
Electrons are released from the tip of the stepped leader
, multiplying rapidly as they accelerate outward, and electrons from the last two steps in the leader strike the ground and produce the TIPPs, which then proceed directly into space.
Forking is an important property of a stepped leader, in which two simultaneous and symmetrical branches emerge.
Caption: Figure 1: Lightning discharge and stepped leader propagation.
Many rocket triggered lightning experiments have been done to study the propagation mechanism of the stepped leader [1-6].
In the Triggering Model, the Dielectric Breakdown Model (DBM) [18-20], which is a stochastic fractal model, is used to simulate the propagation of the stepped leader. To solve the problem of floating conductor, a charge conservation equation is introduced to describe the triggering wire.
The stepped leader
is an advancing column of ionization that intermittently zig-zags its way to the ground (or a zone of opposite charge in another cloud).
For an example, A the definition of the beginning of the stepped leader
field variation is a common confusion among scientists.
After electrical charges separate in a thundercloud, a channel of ionized gas, the "stepped leader
," begins to carve through the air.
Cloud-to-ground strikes occur in steps: first, a stepped leader
begins a branched downward thrust to the ground, then a return stroke flashes from the ground back up the channel created by the leader.
As a negative stepped leader
approaches the ground, positive charges are induced at the ground and by tall conducting features, thereby maintaining the electrical potential between leader and ground.
In the instant before the lightning strike, stepped leaders
begin working their way downward from the cloud charge in 150-foot jumps.