Why are lightning bolts jagged instead of straight?
Because air is normally an electrical insulator, it must break down so that the conductive channel can form in order for a lightning flash to occur. This breakdown of the air between the cloud and the ground does not happen all at once, however. Instead, it happens in discrete steps of about 50 meters, with each step taking about one microsecond and about 50 microseconds elapsing between steps. Because of the discrete nature of this process, the initial channel of a lightning flash is called a stepped leader.
Although the formation of a lightning channel is a result of the attraction between negative charge in the cloud and positive charge induced in the ground, the individual steps are often far from vertical. This variability arises because the conductivity of the air is not uniform. The channel will tend to extend out to regions of higher conductivity. As a result, the relatively short step size and the random distribution of such regions of higher conductivity render the channel jagged rather than smooth. Also, the point where the channel contacts the ground may be displaced a considerable distance horizontally from the point inside the cloud where the channel began.
(Answer courtesy of Scientific American Magazine)
Because air is normally an electrical insulator, it must break down so that the conductive channel can form in order for a lightning flash to occur. This breakdown of the air between the cloud and the ground does not happen all at once, however. Instead, it happens in discrete steps of about 50 meters, with each step taking about one microsecond and about 50 microseconds elapsing between steps. Because of the discrete nature of this process, the initial channel of a lightning flash is called a stepped leader.
Although the formation of a lightning channel is a result of the attraction between negative charge in the cloud and positive charge induced in the ground, the individual steps are often far from vertical. This variability arises because the conductivity of the air is not uniform. The channel will tend to extend out to regions of higher conductivity. As a result, the relatively short step size and the random distribution of such regions of higher conductivity render the channel jagged rather than smooth. Also, the point where the channel contacts the ground may be displaced a considerable distance horizontally from the point inside the cloud where the channel began.
(Answer courtesy of Scientific American Magazine)