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Lightning Safety Program
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Understanding Lightning:
Return Stroke

graphic illustrating text
Figure 1

The return stroke is the very bright visible flash that we see as lightning, caused by the rapid discharge of electricity. Once the step leader makes contact with a streamer, the negative charge that has accumulated along the leader channel flows rapidly to ground. The movement of the charge starts at the point of contact and rapidly works its way upward as charge is drained from the channel
(Figure 1.

Although the visible flash is associated with the rapid movement of charge downward, the actual flash propagates upward throughout the channel as the negative charge starts moving toward the ground
(Figure 2).

graphic illustrating text
Figure 2

This is similar to cars that have been stopped by an open drawbridge. Once the drawbridge is opened for traffic, cars initially start moving forward toward the bridge but movement across the bridge works its way backward through the line of stopped cars. For a moment after the initial return stroke, the channel remains conductive and can be a favored path for subsequent downward leaders.

Learn about Subsequent Dart Leaders and Return Strokes or Return to Contents page

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