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If the subsequent dart leader takes a slightly different route to the ground, so-called forked lightning results with the return stroke.

The lightning bolt, called a return stroke, actually travels from the ground into the cloud.

The return stroke on this leader gives the lightning a flickering appearance.

Observation of a gamma-ray flash at ground level in association with a cloud-to-ground lightning return stroke.

The piston’s return stroke then expels the gas and the now-cooled heat-transfer liquid.